Bug 12662: Ajax-based check in does not work for some system preference settings...

Bug 12662: Ajax-based check in does not work for some system preference settings enabled

To reproduce:

- enable "InProcessingToShelvingCart" or "ReturnToShelvingCart"
system preference,
- for a sample patron with 1+ checkouts, try to check in some item[s]
using checkboxes in the "Check in" column in the checkouts table
which is displayed in the "Check out" or "Details" patron account tabs,
- observe that clicking "Renew or return checked items" button only
results in ajax "spinning wheel" stuck in infinite loop; check-in
operation is not performed.

To test:

- follow the steps above to reproduce this bug
- apply patch
- redo the test; ensure that this issue is no longer reproductible.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>