Comment 4 for bug 1605804

Reviewed: https://review.openstack.org/352344
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=f0dd4d6bdd286ea155cf55eb62662993577d8892
Submitter: Jenkins
Branch: master

commit f0dd4d6bdd286ea155cf55eb62662993577d8892
Author: Markus Zoeller <email address hidden>
Date: Mon Aug 8 12:46:43 2016 +0200

    Fix corrupt "host_aggregates_map" in host_manager

    A host can be in multiple host-aggregates at the same time. When a
    host gets removed from an aggregate in thread A and this aggregate
    gets deleted in thread B, there can be a race-condition where the
    mapping data in the host_manager can get out of sync for a moment.

    This change simulates this condition in a unit test and fixes the bug
    by iterating over the mapping itself instead of the out-of-date list
    "aggregates.hosts".

    Closes-Bug: 1605804
    Change-Id: I59861f03f0c681f7118782fb017af377e07552aa