tests: Add reproducer for bug #1879878
tests: Add reproducer for bug #1879878

When one resizes a pinned instance, the instance claims host CPUs for
pinning purposes on the destination. However, the host CPUs on the
source are not immediately relinquished. Rather, they are held by the
migration record, to handle the event that the resize is reverted. It is
only when one confirms this resize that the old cores are finally
relinquished.

It appears there is a potential race between the resource tracker's
periodic task and the freeing of these resources, resulting in attempts
to unpin host cores that have already been unpinned. This test
highlights that bug pending a fix.

Change-Id: Ie092628ac71eb87c9dfa7220255a2953ada9e04d
Signed-off-by: Stephen Finucane <4725dc7f3632bf126d9fbdc30c347e91e8d2fe16@redhat.com>
Related-Bug: #1879878

openstack/nova,klmitch/nova,openstack/nova,mahak/nova,mahak/nova,klmitch/nova,klmitch/nova,klmitch/nova,openstack/nova,mahak/nova