Replace assertEqual(None, *) with assertIsNone in tests

Replace assertEqual(None, *) with assertIsNone in tests to have
more clear messages in case of failure.

Change-Id: Ifbb144e26b62790d8b8ba9b5c3eea7d04844ee19
Closes-Bug:#1280522
Merge "Replace assertEqual(None, *) with assertIsNone in tests"