Comment 11 for bug 1678326

Reviewed: https://review.openstack.org/452363
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=01fa555b36055c1042e342d9f332f38e106d5d0d
Submitter: Jenkins
Branch: stable/ocata

commit 01fa555b36055c1042e342d9f332f38e106d5d0d
Author: Matt Riedemann <email address hidden>
Date: Fri Mar 31 19:56:14 2017 -0400

    Add regression test for quota decrement bug 1678326

    This was spotted from someone validating the fix for
    bug 1670627. They reported that even though they failed
    to delete an instance in ERROR state that was in cell0,
    the quota usage was decremented.

    This is because we committed the quota reservation
    to decrement the usage before actually attempting to destroy
    the instance, rather than upon successful deletion.

    The rollback after InstanceNotFound is a noop because of
    how the Quotas.rollback method noops if the reservations
    were already committed. That is in itself arguably a bug,
    but not fixed here, especially since the counting quotas
    work in Pike will remove all of the reservations commit and
    rollback code.

    Change-Id: I12d1fa1a10f9014863123ac9cc3c63ddfb48378e
    Partial-Bug: #1678326
    (cherry picked from commit 032937ce51c64e0f5292ca3149e3b244863fffca)