Support vg.up call for latest python-vagrant

The call to "up" vagrant has changed to accomodate the provisioner as the
second argument and the vm_name as the third argument. Fixed this by passing
vm_name as a named parameter.

The commit related to this is https://github.com/todddeluca/python-vagrant/commit/bc344ba108ae71d6e2dc48d4f469db5d830765f8