avoid work_results and work release race

* Unsure exactly why this happens but there seems to be a race condition
  related to the time window between Receptor work_results and work
  release. This sleep extends that window and hopefully avoids the race
  condition.

awx/main/tasks.py

@@ -3146,6 +3146,7 @@ class AWXReceptorJob:
                     except Exception:
                         raise RuntimeError(detail)
 
+        time.sleep(3)
         return res
 
     # Spawned in a thread so Receptor can start reading before we finish writing, we