Fix waiting for tasks

The change to avoid duplicate tasks in a queue had an error where
it would cause all tasks to be immediately marked as completed.
This caused the synchronous task waits on actions such as immediate
sync of a single change to return early, before actual completion.

This may have caused other errors as well.

Change-Id: Ie000a1242db17b1bed8c2eac919e242225f5bba6

gertty/sync.py

@@ -64,13 +64,16 @@ class MultiQueue(object):
         return count
 
     def put(self, item, priority):
+        added = False
         self.condition.acquire()
         try:
             if item not in self.queues[priority]:
                 self.queues[priority].append(item)
+                added = True
             self.condition.notify()
         finally:
             self.condition.release()
+        return added
 
     def get(self):
         self.condition.acquire()