@Gustavo, 

I can't reproduce your problem, this patch works well for me. I did two experiments.

One experiment is WITHOUT multipath-tools patch [1] + WITHOUT this os-brick patch, the test result can refer the link [2], we can see that multipath device can be deleted by 'multipath -r'.

Mar 22 10:33:52 juju-zhhuabj-machine-9 nova-compute[22305]: 2017-03-22 10:33:52.233 22305 WARNING os_brick.initiator.linuxscsi [req-0536068d-110c-43a4-82e4-941cdb715042 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] Couldn't find multipath device /dev/mapper/360000000000000000e00000000010001
 
Another experiment is WITHOUT multipath-tools patch [2] + WITH this os-brick patch, the test result can refer the link [3], we can see that multipath device doesn't be delete because this os-brick patch has removed 'multipath -r'.

Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.520 17329 DEBUG oslo_concurrency.lockutils [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] Lock "connect_volume" acquired by "os_brick.initiator.connector.disconnect_volume" :: waited 0.001s inner /usr/lib/python2.7/dist-packages/oslo_concurrency/lockutils.py:273
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.523 17329 DEBUG oslo_concurrency.processutils [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] Running cmd (subprocess): sudo nova-rootwrap /etc/nova/rootwrap.conf multipath -ll /dev/sda execute /usr/lib/python2.7/dist-packages/oslo_concurrency/processutils.py:344
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.705 17329 DEBUG oslo_concurrency.processutils [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] CMD "sudo nova-rootwrap /etc/nova/rootwrap.conf multipath -ll /dev/sda" returned: 0 in 0.183s execute /usr/lib/python2.7/dist-packages/oslo_concurrency/processutils.py:374
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.707 17329 DEBUG os_brick.initiator.connector [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] multipath ['-ll', u'/dev/sda']: stdout=360000000000000000e00000000010001 dm-0 IET,VIRTUAL-DISK
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: size=1.0G features='0' hwhandler='0' wp=rw
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: |-+- policy='round-robin 0' prio=1 status=active
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: | `- 4:0:0:1 sda 8:0  active ready running
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: `-+- policy='round-robin 0' prio=1 status=enabled
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]:   `- 5:0:0:1 sdb 8:16 active ready running
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]:  stderr= _run_multipath /usr/lib/python2.7/dist-packages/os_brick/initiator/connector.py:1286
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.709 17329 DEBUG os_brick.initiator.linuxscsi [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] remove multipath device /dev/sda remove_multipath_device /usr/lib/python2.7/dist-packages/os_brick/initiator/linuxscsi.py:123
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.710 17329 DEBUG oslo_concurrency.processutils [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] Running cmd (subprocess): sudo nova-rootwrap /etc/nova/rootwrap.conf multipath -l /dev/sda execute /usr/lib/python2.7/dist-packages/oslo_concurrency/processutils.py:344
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.826 17329 DEBUG oslo_concurrency.processutils [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] CMD "sudo nova-rootwrap /etc/nova/rootwrap.conf multipath -l /dev/sda" returned: 0 in 0.116s execute /usr/lib/python2.7/dist-packages/oslo_concurrency/processutils.py:374
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.829 17329 DEBUG os_brick.initiator.linuxscsi [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] Found multipath device = /dev/mapper/360000000000000000e00000000010001 find_multipath_device /usr/lib/python2.7/dist-packages/os_brick/initiator/linuxscsi.py:301
Mar 22 11:06:20 juju-zhhuabj-machine-9 nova-compute[17329]: 2017-03-22 11:06:20.829 17329 DEBUG os_brick.initiator.linuxscsi [req-bbcf6687-4e5d-4748-9887-726ff8489008 3f685b7c349c4734afc1a9a87968aca5 52bc463e2bbd46c792ca0d17effd2a86 - - -] multipath LUNs to remove [{'device': '/dev/sda', 'host': '4', 'id': '0', 'channel': '0', 'lun': '1'}, {'device': '/dev/sdb', 'host': '5', 'id': '0', 'channel': '0', 'lun': '1'}] remove_multipath_device /usr/lib/python2.7/dist-packages/os_brick/initiator/linuxscsi.py:127

[1] https://bugs.launchpad.net/ubuntu/+source/multipath-tools/+bug/1621340
[2] http://paste.ubuntu.com/24227639/
[3] http://paste.ubuntu.com/24227824/