Explicitly return NO CONTENT type response for http DELETE request

Change-Id: I920084b92197bb1687e7d978ad350b2e1290ecbc
diff --git a/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/PortChainWebResource.java b/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/PortChainWebResource.java
index 81e2940..d5948cc 100644
--- a/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/PortChainWebResource.java
+++ b/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/PortChainWebResource.java
@@ -146,10 +146,11 @@
      * Delete details of a specified port chain id.
      *
      * @param id port chain id
+     * @return 204 NO CONTENT
      */
     @Path("{chain_id}")
     @DELETE
-    public void deletePortPain(@PathParam("chain_id") String id) {
+    public Response deletePortPain(@PathParam("chain_id") String id) {
         log.debug("Deletes port chain by identifier {}.", id);
         PortChainId portChainId = PortChainId.of(id);
 
@@ -158,5 +159,6 @@
         if (!issuccess) {
             log.debug("Port Chain identifier {} does not exist", id);
         }
+        return Response.noContent().build();
     }
 }