Comment 2 for bug 1771860

Reviewed: https://review.openstack.org/567701
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=0ed68c76fa8a84d1d5f0ab945e34c8e16341d627
Submitter: Zuul
Branch: master

commit 0ed68c76fa8a84d1d5f0ab945e34c8e16341d627
Author: Matt Riedemann <email address hidden>
Date: Thu May 10 19:27:36 2018 -0400

    Update instance.availability_zone during live migration

    While triaging bug 1768876 there was some concern
    that change I8d426f2635232ffc4b510548a905794ca88d7f99
    in Pike had regressed some behavior where a user that
    does not explicitly request a specific AZ during server
    create is then later restricted to only move operations
    within that same AZ.

    This test shows that is not a regression because the
    AvailabilityZoneFilter looks at RequestSpec.availability_zone
    rather than instance.availabililty_zone, so the instance
    is free to be moved across zones.

    As a result of the test, however, it was noticed that
    the instance.availability_zone isn't updated during live
    migration once the destination host is selected. The other
    move operations like unshelve, evacuate and cold migrate
    all update the instance.availabiltiy_zone, so this copies
    the same logic.

    Change-Id: I9f73c237923fdcbf4096edc5aedd2c968d4b893e
    Closes-Bug: #1771860
    Related-Bug: #1768876