[Cake] Update kernel version check in cake

[Jonathan Morton]

I actually had the version check fix locally, but for some reason it hadn't
been picked up by a push yet.

Squashing would involve writing to the TOS byte, which is already done by
ECN marking, via a helper function.

I tried removing the cow stuff once before.  Everything promptly stopped
working until I put it back.  I have no idea why.

- Jonathan Morton
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.bufferbloat.net/pipermail/cake/attachments/20150929/dfffe816/attachment-0002.html>