Fix #1226 UA_Server_addDataSourceVariableNode always returned GOOD

src/server/ua_services_nodemanagement.c

@@ -1247,7 +1247,7 @@ UA_Server_addDataSourceVariableNode(UA_Server *server, const UA_NodeId requested
                                           &typeDefinition, false);
     if(retval != UA_STATUSCODE_GOOD || deleteNodeId)
         UA_NodeId_deleteMembers(outNewNodeId);
-    return UA_STATUSCODE_GOOD;
+    return retval;
 }
 
 static UA_StatusCode