Replace direct use of testtools BaseTestCase.
Replace direct use of testtools BaseTestCase.

Using the BaseTestCase across the tests in the tree lets us put in log
fixtures and consistently handle mox and stubout.

Part of blueprint grizzly-testtools.

Change-Id: Iba7eb2c63b0c514009b2c28e5930b27726a147b0

FlaPer87/oslo.text