When using nginx to terminate TLS (like it's done in Bifrost), it's more
secure to use a Unix socket for communication, so that local users
cannot access plain text communication.
Copies Inspector change I37b762cca035b5855deb92635c29e8eb97a87c20.
Change-Id: If00e5a3537b8fbaae3fa01f71bd515399464da36