Comment 7 for bug 1715182

Reviewed: https://review.openstack.org/509923
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=81c4c17f2a0b9cd3a4d27c0b06092ef456c8979f
Submitter: Zuul
Branch: stable/pike

commit 81c4c17f2a0b9cd3a4d27c0b06092ef456c8979f
Author: Matt Riedemann <email address hidden>
Date: Tue Sep 26 17:03:12 2017 -0400

    Add recreate test for live migrate rollback not cleaning up dest allocs

    We rollback from a failed live migration in two cases:

    1. The pre_live_migration on the destination host fails. The
       _do_live_migration method calls _rollback_live_migration
       explicitly to cleanup the dest host.

    2. The live migration in the virt driver fails, and the virt driver
       calls back to _rollback_live_migration in the ComputeManager.

    Either way, the instance is not on the destination host, so just like
    how we remove volume connections and unplug vifs from the destination
    host, we need to also remove allocations for the destination node in
    Placement.

    This change adds a test to show that we are not currently cleaning up
    allocations on the destination node when we rollback from a live
    migration failure.

    Change-Id: Icbd5d7ff41aa04f8f7934fdce9668762691a4a69
    Related-Bug: #1715182
    (cherry picked from commit 6c3a58ce8001c588fe225d60ec198c7141d74700)