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 assertEqual(0, mock.call_count) instead.
This patch also fixes a typo.

Change-Id: I7cfb968f6d4b775ceb901411ee8f24057d97cf91
Merge "Fix calls to mock.assert_not_called()"