Switch to "topics" keyword for messaging driver

The keyword "topic" has been dropped [1] in oslo.messaging. Let's
switch to "topics".

[1] https://review.openstack.org/#/c/433950/

Change-Id: I70012bba09940a5f9a379706b4fc6b901ac9fa02

osprofiler/drivers/messaging.py

@@ -30,7 +30,7 @@ class Messaging(base.Driver):
 
         self.client = messaging.Notifier(
             transport, publisher_id=self.host, driver="messaging",
-            topic="profiler", retry=0)
+            topics=["profiler"], retry=0)
 
     @classmethod
     def get_name(cls):

osprofiler/tests/unit/drivers/test_messaging.py

@@ -36,7 +36,7 @@ class MessagingTestCase(test.TestCase):
 
         messaging.Notifier.assert_called_once_with(
             transport, publisher_id=host, driver="messaging",
-            topic="profiler", retry=0)
+            topics=["profiler"], retry=0)
 
         info = {
             "a": 10,