Unhide /dev/zfs in devfsrules_jail.
Unhide /dev/zfs in devfsrules_jail.

The /dev/zfs device is required for managing jailed ZFS datasets.

Discussed with:	pjd, jamie
MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase