Stop all tasks on shutdown

This stops all of the working jobs when turbo-hipster is closing down

Change-Id: Ic160f75bd8222b233f81d269e4c035f95be11e47
diff --git a/turbo_hipster/worker_manager.py b/turbo_hipster/worker_manager.py
index d011a03..0dcdaaf 100644
--- a/turbo_hipster/worker_manager.py
+++ b/turbo_hipster/worker_manager.py
@@ -79,7 +79,7 @@
         """ Handle the requested job """
         try:
             job_arguments = json.loads(job.arguments.decode('utf-8'))
-            self.tasks[job_arguments['name']].stop_worker(
+            self.tasks[job_arguments['name']].stop_working(
                 job_arguments['number'])
             job.sendWorkComplete()
         except Exception as e:
@@ -128,6 +128,8 @@
 
     def stop(self):
         self._stop.set()
+        for task in self.functions.values():
+            task.stop_working()
         # Unblock gearman
         self.log.debug("Telling gearman to stop waiting for jobs")
         self.gearman_worker.shutdown()