Bug 19530: Prevent multiple transfers from existing for one item

Bug 19530: Prevent multiple transfers from existing for one item

We have found multiple open branch transfers for a given item. While I'm not sure how it is happening at this point, it seems that it would make sense to cancel any existing branch transfers when initiating a new one.

Test Plan:
1) prove t/db_dependent/Circulation/transfers.t

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>