Fix fetchEvent function to fetch by event topic

Change-Id: I8b08367a24ad61b4d805562412de2f70754d40cd
diff --git a/src/controllers/eventrouter.js b/src/controllers/eventrouter.js
index 6cad7a3..5469fc2 100644
--- a/src/controllers/eventrouter.js
+++ b/src/controllers/eventrouter.js
@@ -378,7 +378,7 @@
 
         logger.log('debug', `workflow run ${workflowRunId}, task ${taskId} fetches an event`);
 
-        let event = workflowRun.dequeueEvent(topic);
+        let event = workflowRun.dequeueEventByTopic(topic);
         if(event) {
             return event;
         }