Bug 8723: Update the reserves table for item-level holds

Bug 8723: Update the reserves table for item-level holds

If an item is moved from a biblio to another, the holds should be
updated too.

See discussion on the bug report for more information.

Test plan:
1/ Place a item-level hold on biblio1
2/ Move the item to biblio2
3/ Confirm that the hold still exists and point to the biblio2

This patch should not change the existing behavior for bib-level holds.

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>