[ONOS-6424] Implement missing equals/hashCode methods in classes used in ResourceStore

Change-Id: Idb55676a4232200e1eae5338618d76bb2ca9b836
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EmptyDiscreteResources.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EmptyDiscreteResources.java
index 55a0e94..d956334 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EmptyDiscreteResources.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EmptyDiscreteResources.java
@@ -63,6 +63,16 @@
     }
 
     @Override
+    public int hashCode() {
+        return INSTANCE.hashCode();
+    }
+
+    @Override
+    public boolean equals(Object object) {
+        return object instanceof DiscreteResources && ((DiscreteResources) object).isEmpty();
+    }
+
+    @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
                 .add("values", ImmutableSet.of())