BUG: VlanID always zero for vSwitch PortGroups

After upgrading vCO 5.5 to 5.5.1 I discovered to my dismay that it is now impossible to retrieve the vlan ID for a traditional portgroup; the reported vlanId is now always '0' (not null or undefined).

This is clearly a bug, and in my case it breaks all sorts of things.

I use the following code, which worked in 5.5:

var hosts=Server.findAllForType("VC:HostSystem");

var host=hosts[0];

allpg=host.config.network.portgroup

for (var n=0; n<allpg.length;n++) {

  spec=allpg[n].spec;

  var pgvlan=spec.vlanId

  pgname=spec.name

  System.log("Portgroup "+pgname+" has vlan "+pgvlan)

}

As of version 5.5.1, the vlan ID returned is always 0.