* handle UID incarnations, shared association state that can be swapped
for new handshakes
* detect that message comes from unknown origin and then initiate new
handshake (handled by InboundHandshake stage)
* simplify the OutboundHandshake stage
* doesn't have to listen for HandshakeRsp replies, it can just listen
to when the uniqueRemoteAddress future is completed, InboundHandshake
stage completes the handshake when it receives HandshakeRsp
* send the HandshakeReq via the control message ingress, instead of
pushing it downstreams, than also means that HandshakeReq is only sent
on the control stream, which is good
* materialization race condition
