Avoid slow File Lock checks when not used

What

Adds guard to prevent looking up every single new commit in git on every push

EE MR: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4548

Why

This was slow and leads to timeouts. Refactoring in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4091 meant that the guard was no longer skipping commit lookup

Acceptance criteria

• EE MR (https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4548)
• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• End-to-end tests pass (package-qa manual pipeline job)

Related

Helps mitigate https://gitlab.com/gitlab-org/gitlab-ce/issues/43281

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/43339