Bug 21652: Only set waitingdate to today if there is no waitingdate already

Bug 21652: Only set waitingdate to today if there is no waitingdate already

1- Find or create a hold with a waitingdate other than today
2- Check the item in to generate a new hold alert
3- Select "Confirm and Print"
4- Verify that the waiting date has changed to the current date
5- Apply patch
6- Try 1-3 again, if a waitingdate already exists it should not change
7. Try an item with no waitingdate, it should properly update to today

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>