Bug 11250: "too many holds" message appears inappropriately

Bug 11250: "too many holds" message appears inappropriately

This patch gives the various reasons precedence in this order:
1) Already in possesion
2) Already on hold
3) Age restricted
4) No items available
5) Too many holds

Test Plan:
1) Attempt to place a hold where both "too many holds" and "no items available" messages display
2) Apply this patch
3) Refresh
4) Note only the "no items available" message displays

Signed-off-by: Heather Braum <hbraum@nekls.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>