Fix EventuallyConsistentMapImpl unit tests.

Change-Id: I5d114bac40c16d0f67330ba2b4b922a4301666b2
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 8c52156..fd05d7f 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
@@ -85,7 +85,7 @@
 
     private final ScheduledExecutorService backgroundExecutor;
 
-    private final ExecutorService broadcastMessageExecutor;
+    private ExecutorService broadcastMessageExecutor;
 
     private volatile boolean destroyed = false;
     private static final String ERROR_DESTROYED = " map is already destroyed";
@@ -188,6 +188,18 @@
         };
     }
 
+    /**
+     * Sets the executor to use for broadcasting messages and returns this
+     * instance for method chaining.
+     * @param executor executor service
+     * @return this instance
+     */
+    public EventuallyConsistentMapImpl<K, V> withBroadcastMessageExecutor(ExecutorService executor) {
+        checkNotNull(executor, "Null executor");
+        broadcastMessageExecutor = executor;
+        return this;
+    }
+
     @Override
     public int size() {
         checkState(!destroyed, mapName + ERROR_DESTROYED);