Pass 404 errors to the browser instead of ignoring it

I have an application where I send the meta tag `prerender-status-code` with 404 value, so that the Prerender-service will generate a 404-response. Unfortunately when this was done, the response from Prerender was ignored, bypassing the Prerender-service and sending a 200-response with the default catch-all template instead of the 404.

I can't find a reliable way of determining if the 404 is because the Prerender-service was not found or from the `prerender-status-code`-field, so in worst case if the case the Prerender-url changes, it will pass the 404 for all pages.

But I guess this is less likely than the application sending 404, and that we can assume it's from the meta tag.