python_SUITE: Increase a timeout in test_exchange_dest and test_topic_dest

[Why]
The `test_topic_dest` test case fails from time to time in CI. I don't
know why as there are no errors logged anywhere. Let's assume it's a
timeout a bit too short.

While here, apply the same change to `test_exchange_dest`.

(cherry picked from commit 5f520b8)

Author: dumbbell

deps/rabbitmq_stomp/test/python_SUITE_data/src/x_queue_name.py

@@ -36,7 +36,7 @@ def test_exchange_dest(self):
                 body='Hello World!')
 
         # check if we receive the message from the STOMP subscription
-        self.assertTrue(self.listener.wait(5), "initial message not received")
+        self.assertTrue(self.listener.wait(30), "initial message not received")
         self.assertEqual(1, len(self.listener.messages))
 
         self.conn.disconnect()
@@ -64,7 +64,7 @@ def test_topic_dest(self):
                 body='Hello World!')
 
         # check if we receive the message from the STOMP subscription
-        self.assertTrue(self.listener.wait(5), "initial message not received")
+        self.assertTrue(self.listener.wait(30), "initial message not received")
         self.assertEqual(1, len(self.listener.messages))
 
         self.conn.disconnect()