Moving Dist flow rule store backup mechanism to use EC Map

Change-Id: I465cc2424004721bf09505ac9cde068884f04940
diff --git a/core/store/dist/src/main/java/org/onosproject/store/ecmap/EventuallyConsistentMapImpl.java b/core/store/dist/src/main/java/org/onosproject/store/ecmap/EventuallyConsistentMapImpl.java
index c2c46fc..8111db8 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/ecmap/EventuallyConsistentMapImpl.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/ecmap/EventuallyConsistentMapImpl.java
@@ -357,6 +357,10 @@
     }
 
     private boolean removeInternal(K key, Timestamp timestamp) {
+        if (timestamp == null) {
+            return false;
+        }
+
         counter.incrementCount();
         final MutableBoolean updated = new MutableBoolean(false);