I can confirm the bug:
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320092] ------------[ cut here ]------------
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320100] WARNING: CPU: 1 PID: 42381 at /build/linux-0uniEn/linux-4.4.0/net/ipv6/addrconf_core.c:159 in6_dev_finish_destroy+0x6b/0xc0()
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320102] Modules linked in: cmac arc4 md4 nls_utf8 cifs fscache xt_statistic sch_htb ebt_ip ebtable_filter xt_nat xt_recent ipt_REJECT nf_reject_ipv4 xt_tcpudp xt_mark xt_comment veth ebtable_nat ebtables ipt_MASQUERADE nf_nat_masquerade_ipv4 xfrm_user xfrm_algo iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 xt_addrtype iptable_filter ip_tables xt_conntrack x_tables nf_nat nf_conntrack br_netfilter bridge stp llc overlay i2c_piix4 8250_fintek input_leds joydev mac_hid serio_raw ib_iser rdma_cm iw_cm ib_cm ib_sa ib_mad ib_core ib_addr sunrpc iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic crct10dif_pclmul crc32_pclmul ghash_clmulni_intel hv_netvsc hv_utils hid_hyperv hv_storvsc hid scsi_transport_fc hyperv_keyboard aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper hyperv_fb cryptd psmouse pata_acpi hv_vmbus floppy fjes
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320149] CPU: 1 PID: 42381 Comm: kworker/u128:3 Not tainted 4.4.0-83-generic #106-Ubuntu
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320151] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090006  05/23/2012
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320155] Workqueue: netns cleanup_net
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320156]  0000000000000286 00000000174b4ae5 ffff880686863ba0 ffffffff813f9513
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320158]  0000000000000000 ffffffff81d75940 ffff880686863bd8 ffffffff81081322
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320160]  ffff88048ff82800 ffff88048ff80000 0000000000000006 ffff880686863ca8
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320162] Call Trace:
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320166]  [<ffffffff813f9513>] dump_stack+0x63/0x90
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320170]  [<ffffffff81081322>] warn_slowpath_common+0x82/0xc0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320172]  [<ffffffff8108146a>] warn_slowpath_null+0x1a/0x20
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320173]  [<ffffffff8181ba0b>] in6_dev_finish_destroy+0x6b/0xc0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320176]  [<ffffffff817f17e6>] ip6_route_dev_notify+0x116/0x130
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320178]  [<ffffffff810a1b1a>] notifier_call_chain+0x4a/0x70
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320180]  [<ffffffff810a1c96>] raw_notifier_call_chain+0x16/0x20
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320182]  [<ffffffff8172f655>] call_netdevice_notifiers_info+0x35/0x60
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320185]  [<ffffffff81739e7d>] netdev_run_todo+0x16d/0x320
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320187]  [<ffffffff8174540e>] rtnl_unlock+0xe/0x10
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320189]  [<ffffffff81732a37>] default_device_exit_batch+0x147/0x170
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320193]  [<ffffffff810c4140>] ? __wake_up_sync+0x20/0x20
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320195]  [<ffffffff8172a892>] ops_exit_list.isra.4+0x52/0x60
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320196]  [<ffffffff8172b8e2>] cleanup_net+0x1c2/0x2a0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320199]  [<ffffffff8109a585>] process_one_work+0x165/0x480
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320201]  [<ffffffff8109a8eb>] worker_thread+0x4b/0x4c0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320202]  [<ffffffff8109a8a0>] ? process_one_work+0x480/0x480
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320204]  [<ffffffff810a0c25>] kthread+0xe5/0x100
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320205]  [<ffffffff810a0b40>] ? kthread_create_on_node+0x1e0/0x1e0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320209]  [<ffffffff81840f0f>] ret_from_fork+0x3f/0x70
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320210]  [<ffffffff810a0b40>] ? kthread_create_on_node+0x1e0/0x1e0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320211] ---[ end trace b549322d7d3fedbf ]---
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320212] ------------[ cut here ]------------
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320214] WARNING: CPU: 1 PID: 42381 at /build/linux-0uniEn/linux-4.4.0/net/ipv6/addrconf_core.c:160 in6_dev_finish_destroy+0x83/0xc0()
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320214] Modules linked in: cmac arc4 md4 nls_utf8 cifs fscache xt_statistic sch_htb ebt_ip ebtable_filter xt_nat xt_recent ipt_REJECT nf_reject_ipv4 xt_tcpudp xt_mark xt_comment veth ebtable_nat ebtables ipt_MASQUERADE nf_nat_masquerade_ipv4 xfrm_user xfrm_algo iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 xt_addrtype iptable_filter ip_tables xt_conntrack x_tables nf_nat nf_conntrack br_netfilter bridge stp llc overlay i2c_piix4 8250_fintek input_leds joydev mac_hid serio_raw ib_iser rdma_cm iw_cm ib_cm ib_sa ib_mad ib_core ib_addr sunrpc iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic crct10dif_pclmul crc32_pclmul ghash_clmulni_intel hv_netvsc hv_utils hid_hyperv hv_storvsc hid scsi_transport_fc hyperv_keyboard aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper hyperv_fb cryptd psmouse pata_acpi hv_vmbus floppy fjes
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320243] CPU: 1 PID: 42381 Comm: kworker/u128:3 Tainted: G        W       4.4.0-83-generic #106-Ubuntu
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320244] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090006  05/23/2012
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320245] Workqueue: netns cleanup_net
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320246]  0000000000000286 00000000174b4ae5 ffff880686863ba0 ffffffff813f9513
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320248]  0000000000000000 ffffffff81d75940 ffff880686863bd8 ffffffff81081322
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320249]  ffff88048ff82800 ffff88048ff80000 0000000000000006 ffff880686863ca8
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320251] Call Trace:
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320252]  [<ffffffff813f9513>] dump_stack+0x63/0x90
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320254]  [<ffffffff81081322>] warn_slowpath_common+0x82/0xc0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320255]  [<ffffffff8108146a>] warn_slowpath_null+0x1a/0x20
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320257]  [<ffffffff8181ba23>] in6_dev_finish_destroy+0x83/0xc0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320258]  [<ffffffff817f17e6>] ip6_route_dev_notify+0x116/0x130
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320259]  [<ffffffff810a1b1a>] notifier_call_chain+0x4a/0x70
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320261]  [<ffffffff810a1c96>] raw_notifier_call_chain+0x16/0x20
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320263]  [<ffffffff8172f655>] call_netdevice_notifiers_info+0x35/0x60
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320264]  [<ffffffff81739e7d>] netdev_run_todo+0x16d/0x320
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320266]  [<ffffffff8174540e>] rtnl_unlock+0xe/0x10
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320268]  [<ffffffff81732a37>] default_device_exit_batch+0x147/0x170
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320270]  [<ffffffff810c4140>] ? __wake_up_sync+0x20/0x20
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320271]  [<ffffffff8172a892>] ops_exit_list.isra.4+0x52/0x60
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320272]  [<ffffffff8172b8e2>] cleanup_net+0x1c2/0x2a0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320274]  [<ffffffff8109a585>] process_one_work+0x165/0x480
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320276]  [<ffffffff8109a8eb>] worker_thread+0x4b/0x4c0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320278]  [<ffffffff8109a8a0>] ? process_one_work+0x480/0x480
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320279]  [<ffffffff810a0c25>] kthread+0xe5/0x100
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320280]  [<ffffffff810a0b40>] ? kthread_create_on_node+0x1e0/0x1e0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320282]  [<ffffffff81840f0f>] ret_from_fork+0x3f/0x70
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320283]  [<ffffffff810a0b40>] ? kthread_create_on_node+0x1e0/0x1e0
Jul 12 16:45:39 k8s-agent-C5675ACA-0 kernel: [117514.320284] ---[ end trace b549322d7d3fedc0 ]---
Jul 12 16:45:41 k8s-agent-C5675ACA-0 kernel: [117515.900045] unregister_netdevice: waiting for lo to become free. Usage count = 0
Jul 12 16:45:55 k8s-agent-C5675ACA-0 kernel: [117529.738221] cbr0: port 38(vethc7364258) entered disabled state
Jul 12 16:45:55 k8s-agent-C5675ACA-0 kernel: [117529.741246] device vethc7364258 left promiscuous mode
Jul 12 16:45:55 k8s-agent-C5675ACA-0 kernel: [117529.741248] cbr0: port 38(vethc7364258) entered disabled state
Jul 12 16:48:37 k8s-agent-C5675ACA-0 kernel: [117690.960920] cbr0: port 17(vethb0a73659) entered disabled state
Jul 12 16:48:37 k8s-agent-C5675ACA-0 kernel: [117690.962674] device vethb0a73659 left promiscuous mode
Jul 12 16:48:37 k8s-agent-C5675ACA-0 kernel: [117690.962676] cbr0: port 17(vethb0a73659) entered disabled state
Jul 12 16:48:38 k8s-agent-C5675ACA-0 kernel: [117691.944188] cbr0: port 30(vethdbd8c14b) entered disabled state
Jul 12 16:48:38 k8s-agent-C5675ACA-0 kernel: [117691.946302] device vethdbd8c14b left promiscuous mode
Jul 12 16:48:38 k8s-agent-C5675ACA-0 kernel: [117691.946305] cbr0: port 30(vethdbd8c14b) entered disabled state
Jul 12 16:48:38 k8s-agent-C5675ACA-0 kernel: [117692.767894] cbr0: port 29(vethf4e3f484) entered disabled state
Jul 12 16:48:39 k8s-agent-C5675ACA-0 kernel: [117692.769790] device vethf4e3f484 left promiscuous mode
Jul 12 16:48:39 k8s-agent-C5675ACA-0 kernel: [117692.769793] cbr0: port 29(vethf4e3f484) entered disabled state
Jul 12 16:51:44 k8s-agent-C5675ACA-0 kernel: [117877.264643] cbr0: port 28(vethf2dbc257) entered disabled state
Jul 12 16:51:44 k8s-agent-C5675ACA-0 kernel: [117877.266622] device vethf2dbc257 left promiscuous mode
Jul 12 16:51:44 k8s-agent-C5675ACA-0 kernel: [117877.266624] cbr0: port 28(vethf2dbc257) entered disabled state
Jul 12 16:56:03 k8s-agent-C5675ACA-0 kernel: [118134.644094] unregister_netdevice: waiting for lo to become free. Usage count = 1
Jul 12 20:42:29 k8s-agent-C5675ACA-0 kernel: [131553.475349] Netfilter messages via NETLINK v0.30.
Jul 12 20:42:29 k8s-agent-C5675ACA-0 kernel: [131553.479905] ctnetlink v0.93: registering with nfnetlink.
Jul 12 22:13:58 k8s-agent-C5675ACA-0 kernel: [    0.000000] Initializing cgroup subsys cpuset
Jul 12 22:13:58 k8s-agent-C5675ACA-0 kernel: [    0.000000] Initializing cgroup subsys cpu
Jul 12 22:13:58 k8s-agent-C5675ACA-0 kernel: [    0.000000] Initializing cgroup subsys cpuacct
Jul 12 22:13:58 k8s-agent-C5675ACA-0 kernel: [    0.000000] Linux version 4.4.0-83-generic (buildd@lgw01-29) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) ) #106-Ubuntu SMP Mon Jun 26 17:54:43 UTC 2017 (Ubuntu 4.4.0-83.106-generic 4.4.70)

Affected multiple VMs running in Azure ( Standard D13 v2 ). 

Trying the  sysctl net.ipv6.conf.all.disable_ipv6=1  workaround for the moment, as it has the least impact in production.