Bug 36362: Only call Koha::Libraries->search() if necessary in Item::pickup_locations

Bug 36362: Only call Koha::Libraries->search() if necessary in Item::pickup_locations

To test:

1) Make sure the following tests pass:
 - t/db_dependent/Koha/Item.t
 - t/db_dependent/Koha/Biblios.t
 - db_dependent/Koha/Biblio.t

Sponsored-by: Gothenburg University Library
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 2c1e95562188a6d93c22055e30d6a5e9d7e50034)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>