Bug 19945: ILSDI - Return the reason a reserve is impossible

Bug 19945: ILSDI - Return the reason a reserve is impossible

Currently, the ILDSI services HoldTitle and HoldItem always return a
"NotHoldable" code is the reserve is impossible. We need to know why

Test plan:

 - Apply this patch
 - Place a hold on a non reservable title using ILS-DI web service
   (http://koha-opac.example.org/cgi-bin/koha/ilsdi.pl?service=HoldTitle&patron_id=1&bib_id=1&request_location=)
 - you should get the reason instead of NotHoldable,
 - Place a hold on a non reservable item using ILS-DI web service
   (http://koha-opac.example.org/cgi-bin/koha/ilsdi.pl?service=HoldItem&patron_id=1&bib_id=1&item_id=1)
 - you should get the reason instead of NotHoldable,

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>