Initial empty value should not force overwrite existing.

Change-Id: Icb474a4b7d56b78238672f3cbb2cded435df98f5
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java
index 785ae31..6b4610c 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java
@@ -55,7 +55,7 @@
                 .withSerializer(SERIALIZER)
                 .build();
 
-        childMap.put(Resource.ROOT.id(), new LinkedHashSet<>());
+        childMap.putIfAbsent(Resource.ROOT.id(), new LinkedHashSet<>());
     }
 
     @Override
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentDiscreteResourceSubStore.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentDiscreteResourceSubStore.java
index 738b8d1..d6eb376 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentDiscreteResourceSubStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentDiscreteResourceSubStore.java
@@ -53,7 +53,7 @@
                 .withSerializer(SERIALIZER)
                 .build();
 
-        childMap.put(Resource.ROOT.id(), DiscreteResources.empty());
+        childMap.putIfAbsent(Resource.ROOT.id(), DiscreteResources.empty());
     }
 
     @Override