Resolve "Geo: cache results in issue and message count being incorrect"

What does this MR do?

For a Geo secondary node, it sets the cache expiration for the issues count to 5 mins instead of defaulting to 2 weeks.

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

Why was this MR needed?

When a new issue is created on the primary, the issue count cache is automatically reset. However there is no easy way to do this on the secondary yet, leaving the issue count wrong for 2 weeks. For now, set the expiration to 5 mins.

For the future, a better solution is to communicate the need for certain cache items to be recalculated, so that it is more immediate. See issue #4070 (closed) for some additional discussion on this.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] API support added
• Tests added for this feature/bug
• Review
  • [-] Has been reviewed by UX
  • [-] Has been reviewed by Frontend
  • Has been reviewed by Backend
  • [-] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• 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

What are the relevant issue numbers?

Closes #4070 (closed)