[ticket/14462] Further speed improvements

- Cache the secondary container
- Only initialize tasks/modules that are being used
- Add timeout error message in the AJAX UI

PHPBB3-14462

phpBB/phpbb/install/module/update_database/task/update.php

@@ -158,7 +158,6 @@ class update extends task_base
 				array_unshift($msg, $e->getMessage());
 
 				$this->iohandler->add_error_message($msg);
-				$this->iohandler->send_response();
 				throw new user_interaction_required_exception();
 			}