Bug 14811: Don't update permanent_location with CART or PROC

Bug 14811: Don't update permanent_location with CART or PROC

The permanent_location should not be set to CART or PROC when the item
is edited.
Otherwise we lost an important info.

Test plan:
0/ Set the ReturnToShelvingCart pref
1/ Create an item with location "on_my_shelf"
2/ Check the item in and out
3/ Look at the DB values, location should be "CART" and
permanent_location unchanged (on_my_shelf)
4/ Edit the item, add a note for instance
5/ Without this patch, the permanent_location is erased with 'CART' and
you have definitely lost the info.
With this patch, the permanent_location is unchanged.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>