Fix a bug when stop program is issue and the program is starting

supervisord.py

@@ -518,7 +518,7 @@
             starlet.forcex(pid, code=ssdef.SS__FORCEX)
         self.process.state = ProcessStates.STOPPING
         if self.timer_item:
-            self.timer_item.cancel
+            self.timer_item.cancel = True
         self.timer_item = TimerItem(TimerItemType.PROC_STOPPING, self)
         timer_queue.put(
             PrioritizedItem(current_tick + self.stopwaitsecs, self.timer_item)