Set priority for grvingt to 201701 so that it is less than grele's (see bug 16466)

data/grid5000/sites/nancy/clusters/grvingt/grvingt.json

@@ -355,6 +355,7 @@
     }
   ],
   "model": "Dell PowerEdge C6420",
+  "priority": "201701",
   "queues": [
     "admin",
     "production"