Review Socket Shutdown

[RxDave]

Ensure that sockets are terminated by the client rather than the server, wherever possible.
Also ensure that observable termination yields deterministic results upon graceful shutdown; e.g., the client termination notification on the server should indicate that the observable terminated, not that the client terminated or that either side was forcibly closed by the remote connection.

[RxDave]

A previous release has vastly improved socket shutdown so that it's graceful and yields the appropriate reason(s). Leaving this item open for now just as a reminder to do a deeper review at some point.