Comment 4 for bug 1785318

Reviewed: https://review.openstack.org/599062
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=6d8426ae59c9c989a38d00ff8c665d5ab129107d
Submitter: Zuul
Branch: stable/rocky

commit 6d8426ae59c9c989a38d00ff8c665d5ab129107d
Author: Matt Riedemann <email address hidden>
Date: Fri Aug 3 16:54:49 2018 -0400

    Fix image-defined numa claims during evacuate

    When evacuating, the API does not send the image_ref
    to the compute so currently the compute manager
    rebuild_instance() method will just pass an empty
    dict for image_meta to the rebuild_claim, which means
    if the server was originally created with an image that
    has numa-related constraints, like hw_numa_nodes, those
    constraints would not be applied to the destination host
    during the evacuate.

    This change simply checks for evacuate if image_ref is
    not provided and pulls the image_meta off the instance
    which was stashed in the instance.system_metadata during
    server create (see get_system_metadata_from_image usage
    in the compute API).

    This fix was ported from the starlingx-staging/stx-nova
    repo commit 71acfeae0.

    Change-Id: If548fa3436174b1eae08cdcf6578020cc0c7b81f
    Closes-Bug: #1785318
    (cherry picked from commit 665ba461f3135857034cf33dd5f427d47fdd155e)