_update_usage_from_migrations doesn't grab instance for migration

[Andrew Laski]

In the resource tracker, when updating usage from migrations, a list of migrations is grabbed and then the first instance is pulled and used for all migration updates. This has the potential for invalid resource tracker updates and also for accessing system_metadata on that instance that doesn't exist.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/25961

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/25961
Committed: http://github.com/openstack/nova/commit/a574af21f81e12ea5fd48ad50bd0535d08fcda24
Submitter: Jenkins
Branch: master

commit a574af21f81e12ea5fd48ad50bd0535d08fcda24
Author: Andrew Laski <email address hidden>
Date: Tue Apr 2 19:24:35 2013 -0400

    Grab instance for migration before updating usage

    Updates _update_usage_from_migrations so that it grabs the instance
    associated with a migration before updating usage.

    Bug 1163622

    Change-Id: I64acef912ae71ea5c7fb66e9fcaafe5750c63eaf

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/grizzly
Review: https://review.openstack.org/27713

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/27713
Committed: http://github.com/openstack/nova/commit/447e4a30050285995a8d8520ad18862f290dc834
Submitter: Jenkins
Branch: stable/grizzly

commit 447e4a30050285995a8d8520ad18862f290dc834
Author: Andrew Laski <email address hidden>
Date: Tue Apr 2 19:24:35 2013 -0400

    Grab instance for migration before updating usage

    Updates _update_usage_from_migrations so that it grabs the instance
    associated with a migration before updating usage.

    Bug 1163622

    Change-Id: I64acef912ae71ea5c7fb66e9fcaafe5750c63eaf
    (cherry picked from commit a574af21f81e12ea5fd48ad50bd0535d08fcda24)