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: Ic1d7886e23bd5e2adf1759ad0a5a31841a4ccfa0
Closes-Bug:#1280522
Merge "Replace assertEqual(None, *) with assertIsNone in tests"