iotests.py: filter out successful output of qemu-img create The only "feature" of this "Formatting ..." line is that we have to update it every time we add new option. Let's drop it. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Message-Id: <20211223160144.1097696-10-vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>