fix(pubsub): Change UA_STATUSCODE_GOOD of retval at initialization

 - Changed status code of retval to UA_STATUSCODE_BADNOTFOUND
   as the API functionality fails to invoke an error even a wrong
   publisherID is subscribed

Change-Id: I7c83223f5b964fb5dda818a3f202249c3cb257ce

src/pubsub/ua_pubsub_reader.c

@@ -182,7 +182,7 @@ checkReaderIdentifier(UA_Server *server, UA_NetworkMessage *pMsg, UA_DataSetRead
 static UA_StatusCode
 getReaderFromIdentifier(UA_Server *server, UA_NetworkMessage *pMsg,
                         UA_DataSetReader **dataSetReader, UA_PubSubConnection *pConnection) {
-    UA_StatusCode retval = UA_STATUSCODE_GOOD;
+    UA_StatusCode retval = UA_STATUSCODE_BADNOTFOUND;
     if(!pMsg->publisherIdEnabled) {
         UA_LOG_INFO(&server->config.logger, UA_LOGCATEGORY_SERVER,
                     "Cannot process DataSetReader without PublisherId");