Add Cloud Networks capabilities

Allows for the addition of Cloud Networks to instances.
Instances will have a public and ServiceNet network by
default. ServiceNet can be removed by passing :no_servicenet
to the network configuration.

config.vm.provider :rackspace do |rs|
  rs.network 'c5eeb8bd-1d9d-48fa-aafa-42fca49fa2e7'
  rs.network :no_servicenet
end