go.crypto/ssh: in {Server,Client}Conn, read session ID from

transport layer.

R=agl, dave
CC=golang-dev
https://golang.org/cl/15870044

ssh/client.go

@@ -152,7 +152,7 @@ func (c *ClientConn) handshake() error {
 	if packet[0] != msgNewKeys {
 		return UnexpectedMessageError{msgNewKeys, packet[0]}
 	}
-	return c.authenticate(result.H)
+	return c.authenticate()
 }
 
 // Verify the host key obtained in the key exchange.