Replace assertEqual(None, *) with assertIsNone
Replace assertEqual(None, *) with assertIsNone

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

Closes-Bug:#1280522
Change-Id: Ib7a24bf7443d9c49e42119c649a32a1e8bd20ba1

kevin-zhaoshuai/zun,kevin-zhaoshuai/zun,kevin-zhaoshuai/zun