rx: Remove the ADAPT_WINDOW code

rx: Remove the ADAPT_WINDOW code

RX still has the remnants of an old mechanism for doing RTT and
congestion window detection. This code is #ifdef'd out using
the ADAPT_WINDOW define, but is pretty much unservicable these days,
as it collides with the TCP style implementation (with ADAPT_WINDOW
enabled, both will attempt to manipulate a connections RTT and
window size)

As the current TCP-style RTT and window calculation seem to work
much better in deployment, and there isn't much hope for us being
able to maintain two different congestion mechanisms, just remove
ADAPT_WINDOW. It is in git, if we ever want it back (not that I
think we ever would).

Change-Id: I4a22354e362fde8021f7d8b19e099a0f7b4fba3b
Reviewed-on: http://gerrit.openafs.org/5737
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>