Comment 17 for bug 1794996

Reviewed: https://review.openstack.org/623355
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=6c7e53e21059f80325d728cf7dee2766da7a9471
Submitter: Zuul
Branch: stable/queens

commit 6c7e53e21059f80325d728cf7dee2766da7a9471
Author: Matt Riedemann <email address hidden>
Date: Fri Sep 28 11:18:14 2018 -0400

    Fix InstanceNotFound during _destroy_evacuated_instances

    The _destroy_evacuated_instances method on compute
    startup tries to cleanup guests on the hypervisor and
    allocations held against that compute node resource
    provider by evacuated instances, but doesn't take into
    account that those evacuated instances could have been
    deleted in the meantime which leads to a lazy-load
    InstanceNotFound error that kills the startup of the
    compute service.

    This change does two things in the _destroy_evacuated_instances
    method:

    1. Loads the evacuated instances with a read_deleted='yes'
       context when calling _get_instances_on_driver(). This
       should be fine since _get_instances_on_driver() is already
       returning deleted instances anyway (InstanceList.get_by_filters
       defaults to read deleted instances unless the filters tell
       it otherwise - which we don't in this case). This is needed
       so that things like driver.destroy() don't raise
       InstanceNotFound while lazy-loading fields on the instance.

    2. Skips the call to remove_allocation_from_compute() if the
       evacuated instance is already deleted. If the instance is
       already deleted, its allocations should have been cleaned
       up by its hosting compute service (or the API).

    The functional regression test is updated to show the bug is
    now fixed.

    Change-Id: I1f4b3540dd453650f94333b36d7504ba164192f7
    Closes-Bug: #1794996
    (cherry picked from commit 05cd8d128211adbbfb3cf5d626034ccd0f75a452)
    (cherry picked from commit 0208d64397731afa829bc08cd7b3b6494f0f05d5)