[READY] Correct CWebUser::loginRequired() ajax logic

For example we have ajax request:

1) We use `CWebUser::$loginRequiredAjaxResponse` and we get 200 + our resonse. JSON for example

2) We do not use `CWebUser::$loginRequiredAjaxResponse` and we get 403 as expected!

Without this fix there is no possible to get 403 for ajax request. So all jQuery.ajax() logic break.