dracut: shutdown processing cannot be completed with endless messages

Issue

• The problem occurs after adding a network namespace on a system that a root filesystem is
  created on a LVM volume. When "systemctl reboot" is executed, the following messages are
  output infinitely at shutdown processing. Therefore shutdown processing cannot be completed.

    <snip>
    [  882.991829] dracut: Disassembling device-mapper devices
    [  882.995695] device-mapper: ioctl: remove_all left 1 open device(s)
    rm: cannot remove '/lib/dracut/hooks/shutdown/30-dm-shutdown.sh': Read-only file system
    [  883.005655] dracut: Disassembling device-mapper devices
    [  883.009431] device-mapper: ioctl: remove_all left 1 open device(s)
    rm: cannot remove '/lib/dracut/hooks/shutdown/30-dm-shutdown.sh': Read-only file system
    [  883.018847] dracut: Disassembling device-mapper devices
    [  883.022800] device-mapper: ioctl: remove_all left 1 open device(s)
    rm: cannot remove '/lib/dracut/hooks/shutdown/30-dm-shutdown.sh': Read-only file system
    <snip>