Remove some unused functions (#711)

* Remove some unused functions

* get_room_events_stream is only used in tests

* is_exclusive_room might actually be something we want

synapse/util/__init__.py

@@ -49,9 +49,6 @@ class Clock(object):
         l.start(msec / 1000.0, now=False)
         return l
 
-    def stop_looping_call(self, loop):
-        loop.stop()
-
     def call_later(self, delay, callback, *args, **kwargs):
         """Call something later