Bug 25690: Remove double usage of 'Reserved' return value

Bug 25690: Remove double usage of 'Reserved' return value

The patch "Bug 19116: Hold not set to waiting after transfer" added a
new meaning to 'Reserved' return value of C4::Reserves::CheckReserves
function. Let's remove double usage and have separate Transferred
return value so we can differentiate between attached and non-attached
holds. This will come useful in future refactorings.

This patch does no changes to the logic except in the
/cgi-bin/koha/circ/branchtransfers.pl and circulation.pl we now give
similarly to waiting state notice about hold being transferred.

To test:
   1) Apply this patch
   2) Create a new item level hold so that pickup library is different
   than where the item is currently. Then return the item so that hold
   is being attached and transferred.
   3) Go to branchtransfers.pl and try to create a new transfer: it
   should prompt you with message "Item is attached to a hold and
   being transferred for XXX" and provide you with option to cancel
   the hold or to ignore the transfer.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit fbef5478325bbc71064f9ecb3c4c50eaed0b223d)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>