Don't return OK for EAP-MSCHAPv2 success/fail

it breaks other things in the server, when we have

	eap {
		ok = return
	}

There is minimal additional cost to doing this
Remove one last check for zero
Track response_window to request->delay.  Addresses #645

We track the min_response_window for all home servers, and
then use that value when setting request->delay.  This lets us
deal more quickly with home servers which need sub-second timers
Set prefix to /32 if it wasn't set