Switched from fixtures to mock to mock out starting RPC consumers

fixtures 2.0.0 broke us wildly, so instead of trying to make it work
with new fixtures, I better just switch the mock to... mock.

Change-Id: I58d7a750e263e4af54589ace07ac00bec34b553a
Closes-Bug: #1567295
(cherry picked from commit 2af86b8f6f)
(cherry picked from commit ee32ea5e2b)

neutron/tests/base.py

@@ -65,10 +65,6 @@ def fake_use_fatal_exceptions(*args):
     return True
 
 
-def fake_consume_in_threads(self):
-    return []
-
-
 def get_rand_name(max_length=None, prefix='test'):
     """Return a random string.
 
@@ -341,9 +337,9 @@ class BaseTestCase(DietTestCase):
 
     def setup_rpc_mocks(self):
         # don't actually start RPC listeners when testing
-        self.useFixture(fixtures.MonkeyPatch(
+        mock.patch(
             'neutron.common.rpc.Connection.consume_in_threads',
-            fake_consume_in_threads))
+            return_value=[]).start()
 
         self.useFixture(fixtures.MonkeyPatch(
             'oslo_messaging.Notifier', fake_notifier.FakeNotifier))