Workhorse should correctly log upstream remote IP when listening on a unix socket

#161 (closed) and !254 (merged) allow Workhorse to correctly report upstream remote IPs when Workhorse is running behind a proxy.

Unfortunately these don't work when Workhorse is listening on a unix socket, which is the default approach used in Omnibus.

@jacobvosmaer-gitlab suggested an approach in gitlab-com/gl-infra/production#477 (comment 103844524)