Comment 8 for bug 1727260

Reviewed: https://review.openstack.org/560690
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=92bd7ea118fec4791b903871cdc95d0cd71583e2
Submitter: Zuul
Branch: stable/pike

commit 92bd7ea118fec4791b903871cdc95d0cd71583e2
Author: Sahid Orentino Ferdjaoui <email address hidden>
Date: Wed Oct 25 05:57:11 2017 -0400

    libvirt: disconnect volume from host during detach

    Under certain failure scenarios it may be that although the libvirt
    definition for the volume has been removed for the instance that the
    associated storage lun on the compute server may not have been fully
    cleaned up yet.

    In case users try an other attempt to detach volume we should not stop
    the process whether the device is not found in domain definition but
    try to disconnect the logical device from host.

    This commit makes the process to attempt a disconnect volume even if
    the device is not attached to the guest.

    Closes-Bug: #1727260
    Signed-off-by: Sahid Orentino Ferdjaoui <email address hidden>

    (cherry picked from commit ce531dd1b763704b9043ddde8e80ac99cd193660)
    (cherry picked from commit d6a072b5c5a3ff9de7f4b42cda517ead17efe561)

    Conflicts:
     nova/tests/unit/virt/libvirt/test_driver.py

    NOTE: The conflicts were due to the newer testcase mocking
    'nova.virt.libvirt.host.Host._get_domain' where the older code calls
    'nova.virt.libvirt.host.Host.get_domain', and also dealing with the
    fact that the older code doesn't pass 'encryption' to
    self._disconnect_volume().

    This latter issue means that we need to move the call to
    encryptor.detach_volume() to ensure it gets called if we hit
    exception.DeviceNotFound when detaching the device from
    the guest. This is similar to the original code proposed
    in https://review.openstack.org/#/c/515008/9/nova/virt/libvirt/driver.py
    but it requires special handling for the scenario where cryptsetup
    tries to destroy a dm-crypt device that has already been destroyed.

    Signed-off-by: Chris Friesen <email address hidden>
    Change-Id: I4182642aab3fd2ffb1c97d2de9bdca58982289d8