WIP vendor gitlab-shell hooks
This is a small step towards vendoring the gitlab-shell hooks #1226 (closed). We still use the configuration data from the "old" gitlab-shell.
It pre-emptively already deletes some parts of gitlab-shell we won't need, because they were causing rspec failures and it doesn't seem worth it to me to fix those failures for components we are never going to use.
In particular I deleted the gitlab-shell/go
directory because that currently only plays a role in accepting SSH sessions -- which is the part of gitlab-shell we don't want in Gitaly.
Edited by Jacob Vosmaer