Make docker registry work with location redirects when external storage is used

## What does this MR do?

Honor `Location:` header when working with local registry.
Location makes it possible to download manifests from external storage.

## What are the relevant issue numbers?

Fixed https://gitlab.com/gitlab-org/gitlab-ce/issues/18477

## Remark

Adding `FollowRedirects` makes that we leak `Authorization:` in followed requests.

That is why it is implemented manually and we are explicitly removing `Authorization` header.

cc @marin @twk3 

See merge request !4677