Add gitlab-sshd support to gitlab-shell image

What does this MR do?

Adding gitlab-sshd support to current gitlab-shell docker image

Related issues

Changes from this MR are used for testing gitlab chart MR. The only problem with gitlab-sshd work that have been found for now is that we need to generate ssh server certificates list for config file. But it seems that it could be solved by ERB config template on chart side

gitlab-org/charts/gitlab!1855 (merged)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated