Bug 14607: Baker & Taylor cover images should be accessible by UPC as well as ISBN

Bug 14607: Baker & Taylor cover images should be accessible by UPC as well as ISBN

Test plan (requires Baker and Taylor cover images to be set up and enabled):
  1. Create a record with an ISBN that does not have a cover and a UPC
     that does. 141985934X/085391174929 is one set that works well.
  2. Verify that the record shows up as "No image available" in the
     following OPAC locations: shelf browser, reviews, lists, search and
     reading record. This will require adding reviews/checkouts/etc. for
     the record in question.
  3. Apply patch.
  4. Check the locations again, and verify that the record now has a
     valid cover image.

Signed-off-by: Alexis Rodegerdts <arodegerdts@wallawallawa.gov>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>