Bug 25421: Remove use of Koha::Libraries->pickup_locations

Bug 25421: Remove use of Koha::Libraries->pickup_locations

The current implementation uses Koha::Libraries->pickup_locations which
is problematic and due to be removed by bug 24368. This patch makes the
trivial change of just searching for libraries that are marked with
pickup_location => 1.

Calls to Koha::Item->pickup_locations and Koha::Biblio->pickup_locations
are as well adapted to the new arrayref return value.

To test:
1. Pick a record with only one item
2. Place a biblio-level hold on it
3. Edit the items: remove the item
4. Go to the Holds tab
=> FAIL: It explodes
5. Apply this patch and restart:
   $ sudo koha-plack --restart kohadev
6. Go back and go to the holds tab again
=> SUCCESS: No failure!
7. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Didier Gautheron <didier.gautheron@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>