rx: Big windows make us sad

rx: Big windows make us sad

The commit which took our Window size to 128 caused rxperf to run
40 times slower than before. All of the recent rx improvements have
reduced this to being around 2x slower than before, but we're still
not ready for large window sizes.

As 1.6 is nearing release, reset back to the old, fast, window size
of 32. We can revist this as further performance improvements and
restructuring happen on master.

Reviewed-on: http://gerrit.openafs.org/2844
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit a99e616d445d8b713934194ded2e23fe20777f9a)
Change-Id: I6080c69ba51c8743b8c48bf0e0b7dd481185688d
Reviewed-on: http://gerrit.openafs.org/2922
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>