Fix calls to mock.assert_not_called()

There is no assert_not_called() method in mock, as described here:

https://code.google.com/p/mock/issues/detail?id=159

Fix these calls to use the mock.called attribute instead.

Closes-Bug: #1316167

Change-Id: I865463244ebfc45e1f940c74e1afbb9084930bb3
Merge "Fix calls to mock.assert_not_called()"