CA-116900: Invoke vif move correctly.

Once everything is plumbed through Hotplug.call_hotplug_script
then we can change it to invoke vif-real directly rather than
try to emulate how udev would call the script with all of the
environment variables set correctly.

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Merge pull request #33 from jonludlam/CA-116900

CA-116900: Invoke vif move correctly.