Several unit tests don't tear down utils.execute mock

[Greg Lucas]

The unit tests are failing intermittently due to mocks that are not properly torn down.

For example:

FAIL: common.test_utils.TestTroveExecuteWithTimeout.test_log_error_when_log_output_on_error_is_true
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/opt/stack/trove/trove/tests/unittests/common/test_utils.py", line 52, in test_log_error_when_log_output_on_error_is_true
    '/usr/bin/foo', log_output_on_error=True)
  File "/opt/stack/trove/.tox/py27/local/lib/python2.7/site-packages/testtools/testcase.py", line 906, in __exit__
    raise AssertionError(error_msg)
AssertionError: ProcessExecutionError not raised.

This issue is caused by another test mocking utils.execute_with_timeout but not removing the mock afterwards.

[Greg Lucas (glucas-q)]

Found this mock without cleanup issue in two places:

trove/tests/unittests/backup/test_backupagent.py
trove/tests/unittests/common/test_utils.py

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/117856

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/117856
Committed: https://git.openstack.org/cgit/openstack/trove/commit/?id=0e47809b81cc444e6995a9690c7d78488e8b6703
Submitter: Jenkins
Branch: master

commit 0e47809b81cc444e6995a9690c7d78488e8b6703
Author: Greg Lucas <email address hidden>
Date: Fri Aug 29 14:18:23 2014 -0400

    Avoid leaking mocks across unit tests

    In several unit tests, add setUp and tearDown logic to make sure that
    mocked functions are restored to their default implementation. Otherwise
    a leaked mock can cause another test to fail intermittently.

    Change-Id: I849a88cab45398592379c54210df2e3a97197c8c
    Closes-Bug: 1363192