Change assertTrue(isinstance()) by optimal assert

Some of tests use different method of assertTrue(isinstance(A, B))
The correct way is to use assertIsInstance(A, B) provided by testtools

Change-Id: Ie21fb409edf558409aa4bf5dfe59893c5b544aa8
1 file changed
tree: 7c53881461bc01582711438b67fd0bdb1e164a30
  1. manila_tempest_tests/