race condition where we were transitioning to 'disconnected' and immediately reconnecting in another thread before the socket.close call occurred. Now we're locking the state machine until the disconnect routine completes.

sleekxmpp/xmlstream/xmlstream.py

@@ -302,7 +302,8 @@ class XMLStream(object):
 		return True
 	
 	def disconnect(self, reconnect=False):
-		if not self.state.transition('connected','disconnected'):
+		with self.state.transition_ctx('connected','disconnected') as locked:
+			if not locked:
 				logging.warning("Already disconnected.")
 				return
 			logging.debug("Disconnecting...")