Comment 26 for bug 1732428

Reviewed: https://review.opendev.org/c/openstack/nova/+/787943
Committed: https://opendev.org/openstack/nova/commit/560414036d9f2ebcfeb8626029d0bd849d6cad44
Submitter: "Zuul (22348)"
Branch: stable/ussuri

commit 560414036d9f2ebcfeb8626029d0bd849d6cad44
Author: Alexandre Arents <email address hidden>
Date: Tue Sep 1 08:26:25 2020 +0000

    Update image_base_image_ref during rebuild.

    In different location we assume system_metadata.image_base_image_ref
    exists, because it is set during instance creation in method
    _populate_instance_for_create

    But once instance is rebuild, all system_metadata image property a dropped
    and replace by new image property and without setting back
    image_base_image_ref.

    This change propose to set image_base_image_ref during rebuild.

    In specific case of shelve/unshelve in Qcow2 backend, image_base_image_ref is
    used to rebase disk image, so we ensure this property is set as instance may
    have been rebuild before the fix was apply.

    NOTE(lyarwood): An additional change is required within the
    ShelvePolicyTestV21 test on stable/ussuri to avoid the system_metadata
    of the fake instance being lazy loaded during the test.

    Related-Bug: #1732428
    Closes-Bug: #1893618
    Change-Id: Ia3031ea1f7db8b398f02d2080ca603ded8970200
    (cherry picked from commit fe52b6c25bebdd1b459c7a59fbb8d9f6de200c9d)