Fix Docker repository sync for local storage

What does this MR do?

When local storage is used we get a direct link without a redirect, it used to work but it was broken by !21068 (merged). It wasn't noticed because this bug was disguised by another small bug - if primaty_api_url was specified with trailing slash it worked well (because Registry does a redirect when it gets double-slash link). This MR fixes both bugs. It should probably be backported.

Also, it seems like Registry sometimes uses a refirect even for local storage, for example, when a blob is mounted in a pool.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

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

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

Related to #196158 (closed)