Trainvm 8/macaddress

Edit the VirtualBox xml file so that VM interfaces will always get new MACAddresses on first boot.

Using "Machine - > Add" from the VirtualBox GUI to add a new VM using the generated *.file will fix the MACAddress issue.

Note: Some VirtualBox users prefer to use the ovf zip file we provide. This PR does not edit the ovf XML file since the results of the hack on virt tools other than vbox are unknown at this time.