Bug 12467 - Lost items marked as not on loan even if they are!

Bug 12467 - Lost items marked as not on loan even if they are!

The cronjob longoverdue.pl does not require that an item marked as lost
be returned automatically, but there is a line in ModItem that
automatically marks the item's onloan as false if itemlost is set!

Test Plan:
1) Mark an item as lost with longoverdue.pl, without --mark-returned
2) Inspect the db, note that items.onloan is now 0
3) Apply this patch
4) Mark repeat step 1
5) Inspect the db, noe that items.onloan is still 1
6) Test marking an item as lost from staff interface,
   ensure there are no regressions.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Patch works according to test plan and fixes a data loss bug.

Some notes:
- This patch would be nicer with a regression test.
- Also checked that returning the item removes lost status and onloan still.
- Tried to test with --mark-returned, but couldn't get it to
  return my item neither with nor without the patch. (see comment on
  bug report)

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>