fix debian sysvinit script fails to restart docker daemon when stopped

Fixes: #44130
Signed-off-by: Yann Autissier <yann.autissier@gmail.com>

contrib/init/sysvinit-debian/docker

@@ -131,7 +131,7 @@ case "$1" in
 	restart)
 		check_init
 		fail_unless_root
-		docker_pid=$(cat "$DOCKER_SSD_PIDFILE" 2> /dev/null)
+		docker_pid=$(cat "$DOCKER_SSD_PIDFILE" 2> /dev/null || true)
 		[ -n "$docker_pid" ] \
 			&& ps -p $docker_pid > /dev/null 2>&1 \
 			&& $0 stop