[rackspace|loadbalancers] Fix requiring nodes during load balancer creation

Fog currently requires you to specify a node when creating a load balancer balancers. However, according to the [documentation](http://docs.rackspace.com/loadbalancers/api/v1.0/clb-devguide/content/Create_Load_Balancer-d1e1635.html), they should not be required. This PR addresses removes that requirement.