doc: specify that `message.socket` can be nulled
The socket property of the IncomingMessage object is nulled on the
server after calling message.destroy() and on the client after a
request completes and the socket is kept alive.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
The socket property of the IncomingMessage object is nulled on the
server after calling message.destroy() and on the client after a
request completes and the socket is kept alive.