I created a centos 6 nfsv4 server, and went through the above recreate procedure with a trusty guest, and could successfully mount, and do file operations with accton.  However after a few minutes, the console hung, and most tasks reported the following stack traces in /var/log/kern.log

INFO: task ls:2101 blocked for more than 120 seconds.
      Not tainted 3.13.0-66-generic #108-Ubuntu
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
ls              D ffff88007fd13180     0  2101   1215 0x00000004
 ffff88007b14d630 0000000000000086 ffff8800374e6000 ffff88007b14dfd8
 0000000000013180 0000000000013180 ffff8800374e6000 ffff88007b14d6b0
 ffff88007ffd1460 0000000000000002 ffffffff812d0ce0 ffff88007b14d6a0
Call Trace:
 [<ffffffff812d0ce0>] ? umh_keys_init+0x20/0x20
 [<ffffffff81728499>] schedule+0x29/0x70
 [<ffffffff812d0cee>] key_wait_bit+0xe/0x20
 [<ffffffff81728c42>] __wait_on_bit+0x62/0x90
 [<ffffffff812d0ce0>] ? umh_keys_init+0x20/0x20
 [<ffffffff81728ce7>] out_of_line_wait_on_bit+0x77/0x90
 [<ffffffff810ab3d0>] ? autoremove_wake_function+0x40/0x40
 [<ffffffff812d10be>] wait_for_key_construction+0x6e/0x80
 [<ffffffff812d160c>] request_key+0x5c/0xa0
 [<ffffffffa027858f>] nfs_idmap_get_key+0xaf/0x1c0 [nfsv4]
 [<ffffffffa0278f8f>] nfs_map_name_to_uid+0xef/0x150 [nfsv4]
 [<ffffffffa0270117>] decode_getfattr_attrs+0xe47/0x14b0 [nfsv4]
 [<ffffffff8101bc79>] ? sched_clock+0x9/0x10
 [<ffffffffa027080c>] decode_getfattr_generic.constprop.102+0x8c/0xf0 [nfsv4]
 [<ffffffffa0270ef0>] ? nfs4_xdr_dec_access+0xa0/0xa0 [nfsv4]
 [<ffffffffa0270f60>] nfs4_xdr_dec_getattr+0x70/0x80 [nfsv4]
 [<ffffffffa013e316>] rpcauth_unwrap_resp+0x86/0xd0 [sunrpc]
 [<ffffffffa0270ef0>] ? nfs4_xdr_dec_access+0xa0/0xa0 [nfsv4]
 [<ffffffffa0130f6f>] call_decode+0x1df/0x870 [sunrpc]
 [<ffffffffa0130d90>] ? call_refreshresult+0x170/0x170 [sunrpc]
 [<ffffffffa0130d90>] ? call_refreshresult+0x170/0x170 [sunrpc]
 [<ffffffffa013bd84>] __rpc_execute+0x84/0x400 [sunrpc]
 [<ffffffffa013ccfe>] rpc_execute+0x5e/0xa0 [sunrpc]
 [<ffffffffa01331d0>] rpc_run_task+0x70/0x90 [sunrpc]
 [<ffffffffa0259646>] nfs4_call_sync_sequence+0x56/0x80 [nfsv4]
 [<ffffffffa0259f2e>] _nfs4_proc_getattr+0xbe/0xd0 [nfsv4]
 [<ffffffffa02604ea>] nfs4_proc_getattr+0x5a/0xd0 [nfsv4]
 [<ffffffffa01e19df>] __nfs_revalidate_inode+0xbf/0x310 [nfs]
 [<ffffffffa01d9af3>] nfs_opendir+0xe3/0x100 [nfs]
 [<ffffffff811bb883>] do_dentry_open+0x233/0x2e0
 [<ffffffffa01d9a10>] ? nfs_readdir_clear_array+0x70/0x70 [nfs]
 [<ffffffff811bbbb9>] vfs_open+0x49/0x50
 [<ffffffff811ccf64>] do_last+0x564/0x1240
 [<ffffffff811cac06>] ? link_path_walk+0x256/0x880
 [<ffffffff8131615b>] ? apparmor_file_alloc_security+0x5b/0x180
 [<ffffffff812d8786>] ? security_file_alloc+0x16/0x20
 [<ffffffff811cdcfb>] path_openat+0xbb/0x650
 [<ffffffff811cf0fa>] do_filp_open+0x3a/0x90
 [<ffffffff8118199e>] ? do_mmap_pgoff+0x34e/0x3d0
 [<ffffffff811dbf77>] ? __alloc_fd+0xa7/0x130
 [<ffffffff811bd6d9>] do_sys_open+0x129/0x280
 [<ffffffff817305ba>] ? do_page_fault+0x1a/0x70
 [<ffffffff811bd864>] SyS_openat+0x14/0x20
 [<ffffffff81734c5d>] system_call_fastpath+0x1a/0x1f

I then went and installed keyutils and retested, and could not reproduce the hung tasks.  At first look this looks to be the endpoint for request_key_and_link out of the kernel.  I will verify this tomorrow, and 

I will look at fixing the dependency tomorrow.

Thank you,