add common cleanup for mocks to BaseTestCase in unit tests

[Ihar Hrachyshka]

BaseTestCase that is used in unit tests does not set mock.patch.stopall as a cleanup function, meaning each unit test that uses mock objects is forced to add its own cleanup. This can be enhanced by setting the cleanup function in the base test class.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/95465

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/95581

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/95581
Committed: https://git.openstack.org/cgit/openstack/oslotest/commit/?id=3f6b7424ffb6e576b50346f338d64cc5e8289e6a
Submitter: Jenkins
Branch: master

commit 3f6b7424ffb6e576b50346f338d64cc5e8289e6a
Author: Ihar Hrachyshka <email address hidden>
Date: Mon May 26 22:06:43 2014 +0200

    Cleanup mock patches on BaseTestCase tearDown()

    Instead of cleaning up any remaining mock patches in each unit test that
    uses them, do it once on BaseTestCase tearDown().

    Change-Id: I121ba554e16d83fc5908bb85afee4940f42dc4eb
    Closes-Bug: 1323214