checkservice: support systemd cgroup v2

for svc in "${services[@]}"; do

	unit_path="$(systemctl -p ControlGroup show "$svc"|cut -f 2 -d=)"

	busname="$(systemctl -p BusName show "$svc"|cut -f 2 -d=)"

	tasks_path="$SYSTEMD_CGROUP_BASE_PATH/$unit_path/tasks"

	[[ -e "$tasks_path" ]] || {

		echo "${c_error}** Unable to get pid of $svc: No tasks file: $tasks_path${c_rst}" >&2

		continue

	}

	# check if unit is in system slice

	# get the right pidfile name

	unset pidfile

	for path in "$SYSTEMD_CGROUP_BASE_PATH$unit_path/cgroup.procs" \

		"$SYSTEMD_CGROUP_BASE_PATH$unit_path/tasks"; do

		[[ -r "$path" ]] && pidfile="$path" && continue

	done

	[[ -z "$pidfile" ]] && echo "${c_error}** Unable to find pid file for $svc." >&2 && continue

	# skip non system units

	(( $user_slice == 0 )) && [[ "$unit_path" =~ /user\.slice/ ]] && continue

	pids=( $(< "$SYSTEMD_CGROUP_BASE_PATH/$unit_path/tasks") )

	# parse pidfile

	pids=( $(< "$pidfile") )

	if (( "${#pids[*]}" == 0 )); then

		echo "${c_error}** Unable to get pid of $svc: Tasks file is empty${c_rst}" >&2

		continue