Now that https://github.com/refraction-networking/gotapdance/pull/89 has
been merged, we can use the upstream gotapdance library directly.

We don't have to use a local stub address for conjure PT bridges since
we are actually connecting to a given destination through a one-hop
phantom proxy.

The conjure PT server simply accepts haproxy connections from an
allowlist of conjure stations.

The first steps towards using Conjure's bidirectional registration API
to get phantom IP addresses to connect to.