Notify user if template upgrade is not required (#12483)

Author: sudo87

server/src/main/java/com/cloud/network/router/VirtualNetworkApplianceManagerImpl.java

@@ -3358,6 +3358,7 @@ private List<Long> rebootRouters(final List<DomainRouterVO> routers) {
                 jobIds.add(jobId);
             } else {
                 logger.debug("Router: {} is already at the latest version. No upgrade required", router);
+                throw new CloudRuntimeException("Router is already at the latest version. No upgrade required");
             }
         }
         return jobIds;