Move git version detection to gitaly from the rails application for usage ping data
Related to https://gitlab.com/charts/gitlab/issues/530
TLDR: For usage ping data, rails application needs to know the version of `git` available. It is done by [Gitlab::Git.version](https://gitlab.com/gitlab-org/gitlab-ee/blob/master/lib/gitlab/usage_data.rb#L151), which essentially uses `git` binary to find out the version.
In CNG environment, unicorn nodes will not have `git` binary in them, only gitaly will do. So, rails application should be talking with Gitaly to find out that information, ideally.
/cc @marin @WarheadsSE @jacobvosmaer\-gitlab
issue