Make sure Unicorn listens on localhost:8080

Some installations from source run into this when upgrading to 8.0.

cc @rspeicher @patricio @dblessing

mentioned in issue gitlab-git-http-server#5 (closed)

mentioned in issue gitlab-git-http-server#6 (closed)

Status changed to merged

mentioned in commit d0e74984

@jacobvosmaer Does this need to go into a patch? Please add it to the regressions issue if so.

@rspeicher I believe we tell people to read the update guides on master. That would mean we do not need to cherry-pick it into 8-0-stable{,-ee}.

@jacobvosmaer I'll do it anyway. For the guides I like to make sure any that relate to that specific stable branch are updated there, just in case.

@rspeicher OK