Use statx to verify that path-based unmounts proceed only if the
mountpoint reported by statx matches the MNTTAB entry reported by
libzfs, aborting the operation if they differ. Align
`zfs umount /path` behavior with `zfs umount dataset`.
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes#17481
