Note about recommended nbd-client version; this doc will change in 0.9.5
First stab into nbd new-style handshake

- Uses port 10809 (IANA reserved port for NBD)
- Negotiation supports new-style handshake (nbd-client >= 2.9.18) both fixed and un-fixed
  - export name
  - list exports
  - abort

This is a work in progress and currently only one export name is supported.