Implement toString()

- add more debug logs

Change-Id: I1541d66f24d2dde0712a4daef081ca1f49951ef8
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/DefaultConsistentMap.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/DefaultConsistentMap.java
index 569fc90..e09b624 100644
--- a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/DefaultConsistentMap.java
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/DefaultConsistentMap.java
@@ -189,6 +189,11 @@
         return javaMap;
     }
 
+    @Override
+    public String toString() {
+        return asJavaMap().toString();
+    }
+
     private static <T> T complete(CompletableFuture<T> future) {
         try {
             return future.get(OPERATION_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);