Bug 23985: (bug 21206 follow-up) Fix checkout list when "Hold pickup library match...

Bug 23985: (bug 21206 follow-up) Fix checkout list when "Hold pickup library match" not set

This patch restores the behavior prior to bug 21206.
If "Hold pickup library match" is "Not set", then
hold_fulfillment_policy equals an empty string.

Test plan:
1. Go to "Circulation and fines rules"
2. Under "Default checkout, hold and return policy", unset "Hold pickup
library match" and Save
3. Place a hold on one item for one patron
4. Try to checkout the same item with another patron

=> Without this patch you the checkout list do not show, and the logs
contain "The method Koha::Item-> is not covered by tests!"
=> With this patch applied you see the checkout list

QA will take care of comparing the statement with the one before bug 21206
and make sure they are equivalent

Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 17d221144605875b6efb1569093b76f412f8aea5)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>