Rack sends extra FIN

[rrs]

Summary

There is a small bug in rack where when closing a connection it will
send an extra FIN. This is because it checks the wrong variable
and should not allow a goto send unless the FIN has never been sent.
A timer will set the ACK_NOW flag.

Test Plan

Use a the attached packetdrill script to make sure the problem goes away.

D16604.pkt2 KBDownload