Bug 17766 - Patron notification does not work with multi item holds

Bug 17766 - Patron notification does not work with multi item holds

This patch fixes notification when same biblio has multiple reserves with same borrower,
introduced in Bug 14695. C4::Reserves::ModReserveAffect uses internal method
_koha_notify_reserve but sends itemnumber and biblionumber instead of record_id.

To test:
Prerequisites:
- One biblio with two items attached
- A patron with hold_filled notification activated
- A letter for HOLD with <<reserves.reserve_id>> in it
1) Place two reservations on same biblio
2) checkin item x on pickup branch, observe patron message generated
3) checkin item y on pickup branch, observe patron message generated
4) note that reserve_id is the same on both messages, which is wrong
5) apply this patch and repeat 1-3
6) now observe notifications have correct (different) reserve_id

Signed-off-by: Hugo Agud <hagud@orex.es>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>