R1:3fdb1a2bc437

Improve behavior for not-yet-created non-cluster repositories

Summary: Fixes T10815. We already recovered reasonably from this for cluster repositories, but not for non-cluster repositories.

Test Plan:
- Viewed cluster and non-cluster empty Git repository.
- Viewed cluster and non-cluster empty Mercurial repository.
- Viewed cluster and non-clsuter empty hosted SVN repository.
- Viewed cluster and non-cluster empty observed SVN repository.

Reviewers: chad

Reviewed By: chad

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