Allow setting environment variables for gitlab-workhorse

At the moment (8.2.1) there is no way to set custom environment variables for gitlab-workhorse in gitlab.rb. After reading http://dave.cheney.net/2015/11/29/a-whirlwind-tour-of-gos-runtime-environment-variables I would like to be able to do so.

@marin I see two options: either a separate gitlab_workhorse['env'] setting, or re-using the gitlab_rails['env']. I am leaning towards having gitlab_workhorse['env']. What do you think?

@jacobvosmaer separate set of settings is the way to go if we end up going with it.

This is about tweaking the Go runtime. Gitlab-workhorse itself uses command line switches, not environmental variables.

Milestone changed to 8.4

Reassigned to @axil

Reassigned to @marin

mentioned in merge request !613 (merged)

Status changed to closed by merge request !613 (merged)

mentioned in commit 79b80764