Remove a method almost duplicated in other method

Change-Id: Idc9bd0cb53696f379fe77b7b30683eb977a597ad
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceSubStore.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceSubStore.java
index d2cecb0..1f51f7b 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceSubStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceSubStore.java
@@ -102,7 +102,8 @@
             return true;
         }
 
-        DiscreteResources newValues = oldValues.remove(values);
+        DiscreteResources requested = DiscreteResources.of(values);
+        DiscreteResources newValues = oldValues.difference(requested);
         return childMap.replace(key, oldValues, newValues);
     }