Disable NGINX response buffering when not proxying

Closes https://gitlab.com/gitlab-org/gitlab-workhorse/issues/78

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/24497

Request NGINX to not buffer our response when it is not coming from Rails.

Reassigned to @nick.thomas

Milestone changed to %8.15

Status changed to merged

Mentioned in commit 1453dbb0

mentioned in merge request !94 (closed)