ONOS-4635:Fix Issue with add flows using flowobjective-forward REST API with incorrect priority

Change-Id: I929918b61aec83c2dc2cdca456dfdb1d2d736c01
diff --git a/core/api/src/main/java/org/onosproject/net/flowobjective/DefaultForwardingObjective.java b/core/api/src/main/java/org/onosproject/net/flowobjective/DefaultForwardingObjective.java
index 84e38af..f83d5e1 100644
--- a/core/api/src/main/java/org/onosproject/net/flowobjective/DefaultForwardingObjective.java
+++ b/core/api/src/main/java/org/onosproject/net/flowobjective/DefaultForwardingObjective.java
@@ -283,6 +283,8 @@
             checkArgument(nextId != null || treatment != null, "Must supply at " +
                     "least a treatment and/or a nextId");
             checkNotNull(appId, "Must supply an application id");
+            checkArgument(priority <= MAX_PRIORITY && priority >= MIN_PRIORITY, "Priority " +
+                    "out of range");
             op = Operation.ADD;
             return new DefaultForwardingObjective(this);
         }