Bug 24295: Remove GetTransfer from Z3950Responder

Bug 24295: Remove GetTransfer from Z3950Responder

Replace the GetTrasfer call in Z3950Responder/Session.pm with a call to
the Koha::Item method 'get_transfer'.

Test plan
1/ Configure your system to use the Z3950 responder
2/ Trigger an item transfer for an item
3/ Search for the item via Z3950 and varify the transfer status is set
4/ Apply the patch
5/ Repeat step 3

Rebased-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>