Bug 3638 Self Check Should Capture Hold Items

Shelf Check was receiving messages saying item was wanted
for a hold but the item was discharged to the shelf
not associated with the hold or transited to
the pickup location. The message was also being sent
on discharge of items when a suitable item had already
been captured.
Checkin now associates the item with the hold and sets
the appropriate data for a correct checkin response

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>