Bug 21231: BlockReturnofLostItems does not prevent lost items being found

Bug 21231: BlockReturnofLostItems does not prevent lost items being found

When the syspref BlockReturnOfLostItems is set to Block, the item is blocked from being returned, but is still considered found -- it's set to lost=0 and a refund is applied to the patron (if circ rules allow). The item can then be checked in a second time and returned as it is no longer lost.

Test Plan:
1) Set an item to lost
2) Set BlockReturnOfLostItems to Block
3) Check the lost item in
4) Checkin  message should say item is lost and cannot be returned
5) Check lost status of item, it should remain unchanged

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>