Revert "Pass through to serve_status when we're not talking to the bouncer host directly"

This doesn't work in preview, because the "load balancer" doesn't
provide the hostname in its /healthcheck requests. We think we can
get away with always returning a 200 on /healthcheck for any host,
so we're going to try that instead.

This reverts commit b97d7505f1494b2963fb8023cc253f7f76c8e9c0.