MBS-3856: Revert MBS-1052 "Amazon should lookup cover art by barcode too"

This partly reverts 609f1cb and ea96414.
MBS-3856: Add ./admin/RemoveBarcodeCoverArtUrls.pl.

This script removes all cover art URLs from releases that were fetched
using barcode.
MBS-3856: Fix ./admin/RemoveBarcodeCoverArtUrls.pl (fixup 9737724).
MBS-3856: Also clean releases where barcode has been removed (fixup 9737724).
Merge remote-tracking branch 'origin/mbs-3856-revert-barcode-search' into beta

* origin/mbs-3856-revert-barcode-search:
  MBS-3856: Also clean releases where barcode has been removed (fixup 9737724).
  MBS-3856: Fix ./admin/RemoveBarcodeCoverArtUrls.pl (fixup 9737724).
  MBS-3856: Add ./admin/RemoveBarcodeCoverArtUrls.pl.
  MBS-3856: Revert MBS-1052 "Amazon should lookup cover art by barcode too"