umount_unneeded() LN#802-807 (tahrpup)

# LN# 802-807 of /initrd/init (tahrpup) - https://www.pearltrees.com/s243a/initrd-init/id19535893/item224276141
# LN# 862-867 of https://github.com/puppylinux-woof-CE/woof-CE/blob/c96d661c2232caef1d69c693de673fb0e54796f8/initrd-progs/0initrd/init#L862 (13 Mar 2018)
umount_unneeded() {
 MTD_PARTS="$(mount | cut -f1 -d' ' | grep '^/dev' | grep -v loop | cut -f3 -d'/')"
 for ONE_PART in $MTD_PARTS;do
  [ "$(echo -n "$KEEPMOUNTED" | grep "$ONE_PART")" ] || umount /dev/$ONE_PART
 done
}