Remove individual cfg.CONF.resets from tests

oslo.config.CONF.reset is added to cleanup in BaseTestCase, so it does
not need to be done by individual test cases.

Change-Id: I5fced5c2d480e78e5bb7cc150f0b653313884456
Closes-Bug: #1291144

neutron/tests/unit/ml2/drivers/brocade/test_brocade_mechanism_driver.py

@@ -45,8 +45,6 @@ class TestBrocadeMechDriverV2(test_db_plugin.NeutronDbPluginV2TestCase):
         for opt, val in ml2_opts.items():
             ml2_config.cfg.CONF.set_override(opt, val, 'ml2')
 
-        self.addCleanup(ml2_config.cfg.CONF.reset)
-
         def mocked_brocade_init(self):
             self._driver = mock.MagicMock()