Added a builder for TransactionContexts

Change-Id: I22b467ed0b1e691f3df4ccc5e414b8f4c3bf18f4
diff --git a/core/api/src/main/java/org/onosproject/store/service/StorageService.java b/core/api/src/main/java/org/onosproject/store/service/StorageService.java
index 91cc273..b836ce8 100644
--- a/core/api/src/main/java/org/onosproject/store/service/StorageService.java
+++ b/core/api/src/main/java/org/onosproject/store/service/StorageService.java
@@ -63,9 +63,9 @@
     AtomicCounterBuilder atomicCounterBuilder();
 
     /**
-     * Creates a new transaction context.
+     * Creates a new transaction context builder.
      *
-     * @return transaction context
+     * @return a builder for a transaction context.
      */
-    TransactionContext createTransactionContext();
+    TransactionContextBuilder transactionContextBuilder();
 }