CAA-60, The query here should be equivalent to the same query in Data::Artwork.

This patch mirrors the changes made to musicbrainz-server in commit a4424e231a6fdb0e18327ef6162015d520d46073.
CAA-60, Revert pointles release_group_meta join in resolve_release_group_cover_art query.
Merge branch 'caa-60'

* caa-60:
  CAA-60, Revert pointles release_group_meta join in resolve_release_group_cover_art query.
  CAA-60, The query here should be equivalent to the same query in Data::Artwork.