Make the API follow the real relations

I'm a little confused by this; the API does follow the real relation, as it does follow the resource/instance/node chain. The UI just ends up leaving out the resource object because there's no information there we need.

I got some clarification: the role node table retrieves the associated resources and then passes the associated nodes into the table:

tuskar_ui/infrastructure/overcloud/views.py:

    def _get_nodes(self, overcloud, role):
        resources = overcloud.resources(role, with_joins=True)
        return [r.node for r in resources]

However, if the node doesn't exist for whatever reason, the table will fail.

The table should retrieve the resources, and then display appropriate defaults if the node does not exist.

Are you planning to work on this?

It's too messed up to fix it in Icehouse. I will fix it in J1

What would be nice to have before that, so I don't do pointless work here:
- figure out what will happen with Overcloud Roles
- take the association to Overcloud Roles from the Heat not from instance image

I wanted to fix smaller failures in this bug cause doing the API properly would do that, I will start another smaller bugs for that.