When inheriting the "snapdev" property to we don't always call
zfs_prop_set_special(): this prevents device nodes from being created in
certain situations. Because "snapdev" is the only *special* property
that is also inheritable we need to call zfs_prop_set_special() even
when we're not reverting it to the received value ('zfs inherit -S').
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes#6131
959f56b993