torture: Fix grace-period rate output

The kvm-again.sh script relies on shell comments added to the qemu-cmd
file, but this means that code extracting values from the QEMU command in
this file must grep out those commment.  Which kvm-recheck-rcu.sh failed
to do, which destroyed its grace-period-per-second calculation.  This
commit therefore adds the needed "grep -v '^#'" to kvm-recheck-rcu.sh.

Fixes: 315957ca ("torture: Prepare for splitting qemu execution from kvm-test-1-run.sh")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm-recheck-rcu.sh

@@ -31,7 +31,7 @@ then
 	echo "$configfile ------- " $stopstate
 else
 	title="$configfile ------- $ngps GPs"
-	dur=`sed -e 's/^.* rcutorture.shutdown_secs=//' -e 's/ .*$//' < $i/qemu-cmd 2> /dev/null`
+	dur=`grep -v '^#' $i/qemu-cmd | sed -e 's/^.* rcutorture.shutdown_secs=//' -e 's/ .*$//'`
 	if test -z "$dur"
 	then
 		: