Bug 27808: Refresh the item object when AddReturn is called

Bug 27808: Refresh the item object when AddReturn is called

This patch changes the original implementation so the item object is
refreshed altogether instead of explicitly pinpointing a specific field
we identified an edge case can leave out from ->store. I propose this
alterate implementation because what this bug highlights is the fact we
don't code thinking calls to things can have side-effects (like this
case, with AddReturn updating the onloan status (and maybe other
things?).

To test:
1. Make sure circ tests pass with and without this patch

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>