Bug 32529: Make Koha::Item->safe_to_delete consider 'P' holds as found

Bug 32529: Make Koha::Item->safe_to_delete consider 'P' holds as found

Currently, the Koha::Item->safe_to_delete method checks (among other things) if there are existing waiting or in-transit holds.

It seems that 'In processing' should block item deletion as well.

This patch implements that.

To test:
1. Apply up to the regression tests
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Item.t
=> FAIL: Boo! Tests fail!
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass!
5. Sign off :-D

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