when a connection enters the ESTBLS state using T/TCP, then window
scaling wasn't properly handled. The fix is twofold.
1) When the 3WHS completes, make sure that we update our window
scaling state variables.
2) When setting the `virtual advertized window', then make sure
that we do not try to offer a window that is larger than the maximum
window without scaling (TCP_MAXWIN).
Reviewed by: davidg
Reported by: Jerry Chen <chen@Ipsilon.COM>