More pylint 2 fixes (#15565)

## Description:

More fixes flagged by pylint 2 that don't hurt to have before the actual pylint 2 upgrade (which I'll submit soon).

## Checklist:
  - [ ] The code change is tested and works locally.
  - [x] Local tests pass with `tox`. **Your PR cannot be merged unless tests pass**

tests/common.py

@@ -355,7 +355,7 @@ def ensure_auth_manager_loaded(auth_mgr):
         store._users = OrderedDict()
 
 
-class MockModule(object):
+class MockModule:
     """Representation of a fake module."""
 
     # pylint: disable=invalid-name
@@ -391,7 +391,7 @@ class MockModule(object):
             self.async_unload_entry = async_unload_entry
 
 
-class MockPlatform(object):
+class MockPlatform:
     """Provide a fake platform."""
 
     # pylint: disable=invalid-name