Process all pending receive events

The previous version of the code received a single object out of the
socket, even if the poller indicated that there was more than one event
to be read. This is inefficient, as increases the processing times of
events, and probably is what led to our failures in the Travis CI tests.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

daliuge-runtime/dlg/manager/node_manager.py

@@ -415,7 +415,9 @@ def _receive_events(self, sock_created):
             except Queue.Empty:
                 pass
 
-            if self._pubsub_running and poller.poll(100):
+            if not self._pubsub_running:
+                break
+            for _ in poller.poll(100):
                 self.deliver_event(sub.recv_pyobj())
         sub.close()