private void removeOrphanedServers(AuthzSubject overlord) {
   final Collection<Server> servers = serverManager.getOrphanedServers();
   if (!servers.isEmpty()) {
     log.info("cleaning up " + servers.size() + " orphaned servers");
   }
   for (Server server : servers) {
     try {
       server = serverManager.getServerById(server.getId());
       serverManager.removeServer(overlord, server);
     } catch (ObjectNotFoundException e) {
       log.warn(e);
       log.debug(e, e);
     } catch (PermissionException e) {
       log.warn(e);
       log.debug(e, e);
     } catch (VetoException e) {
       log.warn(e);
       log.debug(e, e);
     }
   }
 }