Revert "in component.py the stop() should do session.leave() and retu…

…rn the future (not return session.leave() result) (#1075)"

This reverts commit 3cd1083.

autobahn/wamp/component.py

@@ -668,7 +668,7 @@ def transport_check(_):
     def stop(self):
         self._stopping = True
         if self._session and self._session.is_attached():
-            self._session.leave()
+            return self._session.leave()
         elif self._delay_f:
             # This cancel request will actually call the "error" callback of
             # the _delay_f future. Nothing to worry about.