Bug 10698: give C4::Circulation::DeleteTransfer() a return value

Bug 10698: give C4::Circulation::DeleteTransfer() a return value

This patch adds return values to DeleteTransfer:
Undef if no parameters are given
1 if a Transfer is deleted
0E0 if a wrong parameter is given

It also fixes some unit tests in t/db_dependent/Circulation_transfers.t

To test:
prove t/db_dependent/Circulation_transfers.t
t/db_dependent/Circulation_transfers.t .. ok
All tests successful.
Files=1, Tests=14, 20 wallclock secs ( 0.03 usr  0.00 sys +  0.39 cusr  0.02 csys =  0.44 CPU)
Result: PASS

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Comment: Applied 10681 and 10692 before 10698
Run prove t/db_dependent/Circulation_transfers.t without errors
No koha-qa errors on all 3 patches

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>