msg/async/AsyncConnection: shorter handshake step deps

msg/async/AsyncConnection: shorter handshake step deps

Originally connect side will wait for accept side sending banner, actually
we don't need this logic to ensure anything.

So connect side will issue banner after tcp handshake straightway. It will
help for reducing session handshake period, then it avoid peer side drop this
connection in low level but connect side don't know right now.

Signed-off-by: Haomai Wang <haomai@xsky.com>