Add attributes to config.yml

node["omf"]["frcp"] defaults to "srv.mytestbed.net"
node["omf"]["uid"] defaults to omf_id from node.json, fall back to
hostname

These attributes can be overwritten via solo.json too. E.g.

{
  "omf": {
    "frcp": "amqp://localhost"
  },
  "run_list": [ "recipe[omf]" ]
}