Add -u option to 'zfs create'

Add -u option to 'zfs create' that prevents file system from being
automatically mounted. This is similar to the 'zfs receive -u'.

Authored by: pjd <pjd@FreeBSD.org>
FreeBSD-commit: freebsd/freebsd@35c58230e292775a694d189ff2b0bea2dcf6947d

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Ported-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #11254