Clients should use only "active" nodes

[futurechimp]

We're going to change things in the next release so that only nodes that are configured properly are included in the active topology returned by the validator directory.

Once we know what the URL path of that route's going to be, we will need to change the Nym clients (and anything topology-related) to get info from the active set, rather than the whole set of registered (but possibly misconfigured) nodes.