[rackspace] add :type to LoadBalancers nodes

http://docs.rackspace.com/loadbalancers/api/v1.0/clb-devguide/content/Nodes-d1e2173.html
Type of node:

PRIMARY – Nodes defined as PRIMARY are in the normal rotation to receive traffic from the load balancer.

SECONDARY – Nodes defined as SECONDARY are only in the rotation to receive traffic from the load balancer when all the primary nodes fail. This provides a failover feature that automatically routes traffic to the secondary node in the event that the primary node is disabled or in a failing state. Note that active health monitoring must be enabled on the load balancer to enable the failover feature to the secondary node.

This is cleaned up and 'works for me'

I used  Charles Proxy to debug traffic generate the gists

https://gist.github.com/hh/d9cbd23097d42db7e531

```ruby
c=Fog::Rackspace::LoadBalancers.new(rackspace_region: :dfw,
  connection_options: {ssl_verify_peer: false, proxy: 'http://localhost:8888'})
[1] pry(main)> lb=s.load_balancers.find {|lb| lb.name == 'testhttp'} 
[2] pry(main)> lb.nodes
=> [  <Fog::Rackspace::LoadBalancers::Node
    id=592343,
    address="72.32.12.183",
    status="OFFLINE",
    weight=1,
    port=80,
    type="PRIMARY",
    condition="ENABLED"
  >,
   <Fog::Rackspace::LoadBalancers::Node
    id=592345,
    address="98.129.97.72",
    status="ONLINE",
    weight=1,
    port=80,
    type="SECONDARY",
    condition="ENABLED"
  >,
   <Fog::Rackspace::LoadBalancers::Node
    id=712997,
    address="10.179.69.183",
    status="OFFLINE",
    weight=1,
    port=80,
    type="PRIMARY",
    condition="ENABLED"
  >]
[3] pry(main)> lb.nodes.last.type="SECONDARY"
=> "SECONDARY"
[4] pry(main)> lb.nodes.last.save
=> true
[5] pry(main)> s.load_balancers.find {|lb| lb.name == 'testhttp'}.nodes
=> [  <Fog::Rackspace::LoadBalancers::Node
    id=592343,
    address="72.32.12.183",
    status="OFFLINE",
    weight=1,
    port=80,
    type="PRIMARY",
    condition="ENABLED"
  >,
   <Fog::Rackspace::LoadBalancers::Node
    id=592345,
    address="98.129.97.72",
    status="ONLINE",
    weight=1,
    port=80,
    type="SECONDARY",
    condition="ENABLED"
  >,
   <Fog::Rackspace::LoadBalancers::Node
    id=712997,
    address="10.179.69.183",
    status="OFFLINE",
    weight=1,
    port=80,
    type="SECONDARY",
    condition="ENABLED"
  >]

```