The Manila test module uses a class called StubOutForTesting, which
is an awkward holdover from when the unit tests were using Mox.
Alex wrote a more elegant and capable mocker method,
manila.test.TestCase.mock_object, in the Cinder project which we
have now added to Manila. So to remove the duplicate functionality
and legacy code, all references to self.stubs.Set() in the Manila
tests should be replaced with self.mock_object() and any related
dead code should be removed.
Resolves-bug: #1415602
Change-Id: Ie5f203c0b2cb57ad00d9ec8db0529075b6fef261
65d1158526