8.0-REL lagg(4) + vlan(4) + em(4) problems

[Jeff Blank]

I wrote:
> I've just upgraded a 7.1-REL server to 8.0-REL and have lost my
> ability to use vlan(4) on top of lagg(4) on top of em(4).

I should have mentioned that I'm using lagg failover.  I can reproduce
my problem in single-user as follows:

# ifconfig em0 up
# ifconfig em1 up
# ifconfig lagg0 create laggproto failover laggport em0 laggport em1 up
# ifconfig vlan20 create vlan 20 vlandev lagg0
# ifconfig vlan20 <ip>/<mask> up

Jeff