Bug 30909: Retain permanent_location if mapped

Bug 30909: Retain permanent_location if mapped

If items.permanent_location is mapped to a MARC subfields we must retain
the value, not using items.location

Test plan:
1 - Map permanent_location to a marc field
2 - Expose that field in the item editor
3 - Change the location of the item and retain the permanent location on saving
4 - note that permanent location has not changed

Test the different other situation, when adding and editing: Empty the field, change only location, change only permanent_location, etc.

Signed-off-by: andrew <andrewfh@dubcolib.org>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>