Geo: Use database-cached status if redis-cached status is unavailable

What does this MR do?

Falls back to database-held values for Geo node status if the redis-held values are not present, in case they're present.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

It addresses an inconsistency between the primary and secondary where a secondary's status is in the database, but the secondary is having trouble generating something and its redis cache is empty. Seen on staging.gitlab.com today.

Screenshots (if relevant)

Fixes this situation:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a Backend maintainer
• EE specific content should be in the top level /ee folder
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?