Set all of the ports into the same vlangroup; there's only one vlangroup
(pvid=1) and we already configure them to send to other ports.

Setting pvid=portnum would mean that there were separate vlangroups
for each ports, but 'leaking' into other ports.  The result? All port
traffic flooded to all other port traffic.

Tested:

* DB120, AR9344 + AR8327 switch