Bug 33639: Make add item to item group work from additem.pl

Bug 33639: Make add item to item group work from additem.pl

To test:

1, Create one or more item groups for a bib if needed
2. Create a new item, and at the bottom of the 'Add item' screen, select the item group to which you want this item added. Save.
3. On the Normal tab, see that the item has not been added to the item group you selected.
4. APPLY PATCH, restart_all
5. Try 1-3 again but this time the item should succesffuly be added to the item group.
6. Add a new item and to the same record and this time try the 'Create a new item group' from the dropdown.
7. Name the new item group.
8. Make sure it is correctly added to the item group.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>