Update Omnibus Fork for CINC 17
The Omnibus gem fork at https://gitlab.com/gitlab-org/omnibus needs updated to move to CINC major version 17.
Deliverables
- Evaluate whether Omnibus gem can be upgraded in addition to changed over to CINC 17
- If upgrading is possible, cut a new stable branch, otherwise, open a merge request against 8.2.1-stable