Add configuration option `networks`, a list of network UUIDs, to attach to the
source instance.
In some openstack installs, no default network will be attached or the network
with the ability to attach a public floating IP will need to be specified.
This change adds base support for an openstack builder.
Thank you to Rackspace for providing cloud assets to complete this work
and @sam-falvo for working with us on the perigee/gophercloud changes.
Mitchell Hashimoto
Ian Delahorne
Kgespada
Mark Peek