Bug 23048: Hide non-pickup branches from hold modification select

Bug 23048: Hide non-pickup branches from hold modification select

When modifying holds in staff client via reserve/request.pl or
the holds-tab in members/moremember.pl, the pickup library dropdown
lists libraries not marked for pickup. Hide those branches,
unless the branch is marked as a pick-up branch for already
existing hold.

The reason for showing a non-pickup branch for the holds created
before the branch was marked as non-pickup: If the non-pickup branch
wasn't shown, the branch in those holds would get set to the first
branch in the select if the hold was modified.

Test plan:
1) Create a hold for a patron, to be picked up from a certain branch.
2) Edit the branch and another branch so they are no longer
   pickup locations.
3) Go to members/moremember.pl for that patron, check the Holds-tab
   Pickup library -drop down. It lists both of the non-pickup branches.
4) Go to reserve/request.pl for that biblio. The hold-table
   Pickup library -drop down lists both of the non-pickup branches.
5) Apply patch.
6) Repeat 3 & 4, drop down no longer lists the non-pickup branch, but
   should still list the branch where the hold was marked to be picked
   from.

Signed-off-by: Pasi Kallinen <pasi.kallinen@koha-suomi.fi>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>