Comment 4 for bug 1771810

Reviewed: https://review.openstack.org/569055
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=77881659251bdff52163ba1572e13a105eadaf7f
Submitter: Zuul
Branch: master

commit 77881659251bdff52163ba1572e13a105eadaf7f
Author: Surya Seetharaman <email address hidden>
Date: Thu May 17 10:16:56 2018 +0200

    Make _instances_cores_ram_count() be smart about cells

    This makes the _instances_cores_ram_count() method only query for instances
    in cells that the tenant actually has instances landed in. We do this by
    getting a list of cell mappings that have instance mappings owned by the
    project and limiting the scatter/gather operation to just those cells.

    Change-Id: I0e2a9b2460145d3aee92f7fddc4f4da16af63ff8
    Closes-Bug: #1771810