[FIX]-a bug in kafka-integration app has been fixed.

Change-Id: Ib6f21acac161da9bbc3cd9b9f42540def64c641b
diff --git a/apps/kafka-integration/app/src/main/java/org/onosproject/kafkaintegration/kafka/KafkaConfigManager.java b/apps/kafka-integration/app/src/main/java/org/onosproject/kafkaintegration/kafka/KafkaConfigManager.java
index 4b90b8e..078b10c 100644
--- a/apps/kafka-integration/app/src/main/java/org/onosproject/kafkaintegration/kafka/KafkaConfigManager.java
+++ b/apps/kafka-integration/app/src/main/java/org/onosproject/kafkaintegration/kafka/KafkaConfigManager.java
@@ -71,7 +71,7 @@
     protected String keySerializer = KEY_SERIALIZER_DEFAULT;
 
     /** Serializer class for value that implements the Serializer interface. */
-    protected String valueSerializer = VALUE_SERIALIZER;
+    protected String valueSerializer = VALUE_SERIALIZER_DEFAULT;
 
     @Activate
     protected void activate(ComponentContext context) {