WIP: Refresh foreign tables fast and safely

What does this MR do?

The idea here is to let reconfigure call rake geo:db:refresh_foreign_tables more often. Then rake geo:db:refresh_foreign_tables can determine whether a refresh is truly needed or not. This must be fast so we don't bog down reconfigure.

It is option 3 of omnibus-gitlab#4672 (comment 218542272):

1. tell omnibus to run the check, and parse it to know if we need refresh
2. or add a rake task that returns 1 if need refresh
3. or guard rake geo:db:refresh_foreign_tables with the check, and always run the task on reconfigure

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

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