We need to be able to garbage collect manifests from Clair in a robust way, even when Quay is not configured to do the garbage collection.

The initial version can use GABI for read access to both Quay and Clair's databases, but because GABI is an AppSRE-ism, the final command needs to be able to consume a "normal" Quay and Clair config and talk to the databases directly.