Bug 19626: Calculate expiration date for existing holds based on waitingdate

Bug 19626: Calculate expiration date for existing holds based on waitingdate

To test:
1 - Have/create a 16.11 instance with some waiting holds
2 - Those holds should not have an expirationdate
3 - Make sure some of the holds are waiting longer than
ReservesMaxPickupDelay
BACKUP THE DB
4 - Upgrade to 17.05 (or later)
5 - Check the expirationdate for the holds
6 - The date wil be in the future (curdate + delay)
7 - Restore DB
8 - Apply patch
9 - Run the upgrade again
10 - expirationdate should now be based on waitingdate

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>