Fix remount when setting multiple properties.

The previous code was checking zfs_is_namespace_prop() only for the
last property on the list. If one was not "namespace", then remount
wasn't called. To fix that move zfs_is_namespace_prop() inside the
loop and remount if at least one of properties was "namespace".

Reviewed-by: Umer Saleem <usaleem@ixsystems.com>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Closes #15000