Currently a lot of tests are using a custom self.store() method to
perform automatic cleanup on tearDown.
We should change to the standard addCleanup method that is being called
on every object (also if setUp fails and tearDown is not called).
See [1] for details.
[1] https://docs.python.org/2/library/unittest.html#unittest.TestCase.addCleanup
Change-Id: Ic62dd9a5e07435d1179793ec2c5cdc6e4eddef60
53db6e21df