fuzzy: clean up scrub stress programs quietly

fuzzy: clean up scrub stress programs quietly

In the cleanup function for online fsck stress test common code, send
SIGINT instead of SIGTERM to the fsstress and xfs_io processes to kill
them.  bash prints 'Terminated' to the golden output when children die
with SIGTERM, which can make a test fail, and we don't want a regular
cleanup function being the thing that prevents the test from passing.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>