Geo: Prevent RegistryFinder calls on the primary

What does this MR do?

Registry tables only exist on Geo secondaries, so at the very least, it's semantically wrong to use RegistryFinders on a Geo primary. I think it used to be fine since the secondary didn't used to take into account the registry tables.

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/11451

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team