Set priority from message properties if not in delivery_info

Add contributor.

CONTRIBUTORS.txt

@@ -191,3 +191,5 @@ Feanil Patel, 2015/05/21
 Jocelyn Delalande, 2015/06/03
 Justin Patrin, 2015/08/06
 Juan Rossi, 2015/08/10
+Piotr Maślanka, 2015/08/24
+Gerald Manipon, 2015/10/19

celery/worker/job.py

@@ -186,7 +186,8 @@ class Request(object):
                 'delivery_info': {
                     'exchange': delivery_info.get('exchange'),
                     'routing_key': delivery_info.get('routing_key'),
-                    'priority': delivery_info.get('priority'),
+                    'priority': properties.get(
+                        'priority', delivery_info.get('priority')),
                     'redelivered': delivery_info.get('redelivered'),
                 }