rcutorture: Save kvm.sh output to log

This commit logs the progress text that kvm.sh outputs, improving
after-the-fact troubleshooting.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --cc tools/testing/selftests/rcutorture/bin/kvm.sh
Simple merge