Comment 21 for bug 1669054

Reviewed: https://review.openstack.org/649319
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=20c1414945db633ed00c1f19f1f0d163028454d9
Submitter: Zuul
Branch: stable/stein

commit 20c1414945db633ed00c1f19f1f0d163028454d9
Author: Matt Riedemann <email address hidden>
Date: Sat Mar 23 12:01:42 2019 -0400

    Add functional regression test for bug 1669054

    Change Ic3968721d257a167f3f946e5387cd227a7eeec6c in Newton
    started setting the RequestSpec.ignore_hosts field to the
    source instance.host during resize/cold migrate if
    allow_resize_to_same_host=False in config, which it is by
    default.

    Change I8abdf58a6537dd5e15a012ea37a7b48abd726579 also in
    Newton persists changes to the RequestSpec in conductor
    in order to save the RequestSpec.flavor for the new flavor.
    This inadvertently persists the ignore_hosts field as well.

    Later if you try to evacuate or unshelve the server it will ignore
    the original source host because of the persisted ignore_hosts value.
    This is obviously a problem in a small deployment with only a few
    compute nodes (like an edge deployment). As a result, an evacuation
    can fail if the only available host is the one being ignored.

    This adds a functional regression recreate test for the bug.

    Change-Id: I6ce2d6b1baf47796f867aede1acf292ec9739d6d
    Related-Bug: #1669054
    (cherry picked from commit 556cf103b22ab6bebecc9d824d6f918cda38fe3e)