Support of VLAN tags

[maniac777]

Libvirt supports vlan aware bridges (bridges with vlan filtering enabled). If it is used and hypervisor have multiple vlans there is only one bridge and you have to pass information about vlan configuration in interface definition in xml ex.:

<vlan>
  <tag id='99'/>
</vlan>

or

<vlan trunk='yes'>
  <tag id='1'/>
  <tag id='9'/>
  <tag id='15'/>
  <tag id='301'/>
</vlan>

I would like to add support of this to FOG and send a patch, and then if it my work will be accepted I'm going to prepare the same for The Foreman that is using this library. It would be nice if someone could stop me if this work is in progress anyway and/or it will not be accepted for reasons I may be not aware at the moment.

[davispuh]

FYI, I actually just finished implementing this for libvirt Network, take a look at #196. Specifically lib/fog/libvirt/models/compute/network/vlan.rb. I don't plan implementing this for server/nic but I think you can just reuse that and should be pretty straightforward.