iotests: Fix test 039

Test 039 used qemu-io -c abort for simulating a qemu crash; however,
abort() generally results in a core dump and ulimit -c 0 is no reliable
way of preventing that. Use "sigraise $(kill -l KILL)" instead to have
it crash without a core dump.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1418032092-16813-4-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
