Bug 30564

When placing a hold in the staff interface, we have one pickup location dropdown at the top of the page for bib-level holds, and then separate dropdowns for the pickup location for an item-level hold. The interface here makes it easy to mistakenly place an item-level hold for the wrong pickup location. 

To recreate:
- go to request.pl
- change the pickup location at the top of the form
- then pick a specific item and click "Place hold"
- Koha ignores the change you made to the bib-level dropdown and maintains the default pickup from the item-level line

When one changes the bib-level pickup, Koha should automatically change all the item-level locations to match the new selection. If that would result in an invalid pickup location, the item should instead go to a blank pickup so the user is forced to pick something.