Make service and monitor permissions checks optional

MaxScale shouldn't require the service and monitor user checks. It makes
sense to disable the checks to speed up the startup process when the user
knows that the permissions are OK.

server/core/dbusers.c

@@ -2689,7 +2689,8 @@ static bool check_server_permissions(SERVICE *service, SERVER* server,
  */
 bool check_service_permissions(SERVICE* service)
 {
-    if (is_internal_service(service->routerModule))
+    if (is_internal_service(service->routerModule) ||
+        config_get_global_options()->skip_permission_checks)
     {
         return true;
     }