For path MTU discovery tcp_mtudisc() should resend a TCP packet by

For path MTU discovery tcp_mtudisc() should resend a TCP packet by
calling tcp_output() if the TCP maximum segment size changes.  But
that did not work, as the new value was compared before tcp_mss()
had a chance to modify it.  Move the comparison and change it from
not equal to greater than.  It makes only sense to resend a packet
immediately if it becomes smaller and is more likely to fit.
OK sashan@ tobhe@