Add limit for getQueueHead call

provider/queue/queue.go

@@ -133,7 +133,7 @@ func (q *Queue) work() {
 }
 
 func (q *Queue) getQueueHead() (*query.Result, error) {
-	qry := query.Query{Orders: []query.Order{query.OrderByKey{}}}
+	qry := query.Query{Orders: []query.Order{query.OrderByKey{}}, Limit: 1}
 	results, err := q.ds.Query(qry)
 	if err != nil {
 		return nil, err