Bug 21020: Fix return branch on transfer - SIP

Bug 21020: Fix return branch on transfer - SIP

Caused by
  commit 546379cc92b733cb29a0b70247a72c770afdad26
  Bug 17680: C4::Circulation - Remove GetItemIssue, simple calls

Since this commit AddReturn return a Koha::Issue object, not a hashref
with item's info.

Test plan:
1 - Enable SIP server on your test instance
   For kohadevbox:
   cp /etc/koha/SIPConfig.xml /etc/koha/sites/kohadev/
   create patron with user/pass term1/term1 and grant circulation
   privileges
2 - enable AutomaticItemReturn
3 - Checkin an item which will generate a transfer via SIP2:
   perl /home/vagrant/kohaclone/misc/sip_cli_emulator.pl -a localhost -p
   6001 -su term1 -sp term1 -l LPL --item {BARCODE} -m checkin -t
   CR
4 - Note no CT field
5 - Apply patch
6 - Repeate checkin via SIP2
7 - Transfer destination is correctly returned in CT

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>