Comment 6 for bug 1724172

Reviewed: https://review.opendev.org/512623
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=9cacaad14e8c18e99e85d9dc04308fee91303f8f
Submitter: Zuul
Branch: master

commit 9cacaad14e8c18e99e85d9dc04308fee91303f8f
Author: Balazs Gibizer <email address hidden>
Date: Tue Oct 17 15:06:59 2017 +0200

    cleanup evacuated instances not on hypervisor

    When the compute host recovers from a failure the compute manager
    destroys instances that were evacuated from the host while it was down.
    However these code paths only consider evacuated instances that are
    still reported by the hypervisor. This means that if the compute
    host is recovered in a way that the hypervisor lost the definition
    of the instances (for example the compute host was redeployed) then
    the allocation of these instances will not be deleted.

    This patch makes sure that the instance allocation is cleaned up
    even if the driver doesn't return that instance as exists on the
    hypervisor.

    Note that the functional test coverage will be added on top as it needs
    some refactoring that would make the bugfix non backportable.

    Change-Id: I4bc81b482380c5778781659c4d167a712316dab4
    Closes-Bug: #1724172