Status check is fetching domain configuration and causing API requests

After enabling gitlab config source for 99% of the domains on staging we started seeing many requests with params like host=gitlab.com coming from Pages to the internal API.

I think these are caused from the status check endpoint (that is being hit by HAProxy). We can reproduce it locally - enable the new config source for 100% of the domains and point your Pages to your local Rails app, you can see that requests to /-/readiness will hit the API and get logged in log/api_json.log.

There is already a short-circuit for this check (https://gitlab.com/gitlab-org/gitlab-pages/-/blob/master/app.go#L128), we should do this earlier or at least not hit the API for this path.