rcutorture: Add cpu0 to the set of CPUs to add jitter

jitter.sh currently does not add CPU0 to the list of CPUs for adding of
jitter. Let us add it to this list even when it is not hot-pluggable.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

tools/testing/selftests/rcutorture/bin/jitter.sh

@@ -36,8 +36,12 @@ do
 
 	# Set affinity to randomly selected online CPU
 	cpus=`grep 1 /sys/devices/system/cpu/*/online |
-		sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
-		grep -v '^0*$'`
+		sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
+
+	# Do not leave out poor old cpu0 which may not be hot-pluggable
+	if [ ! -f "/sys/devices/system/cpu/cpu0/online" ]; then
+		cpus="0 $cpus"
+	fi
 
 	cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
 		srand(n + me + systime());