rxperf: Fix so it builds on Unix

rxperf: Fix so it builds on Unix

Fix assorted errors in the rxperf utility so that it will build
on Unix.

Reviewed-on: http://gerrit.openafs.org/2834
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit a10f644fd21482559039f79e4a14fd39a83f6f9b)
(cherry picked from commit a421dbb79a96e6ac4ca004c6b65ace313c340c3f)
Change-Id: I80532b781fe758112718ab8d5b268e4005d4376d
Reviewed-on: http://gerrit.openafs.org/2916
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>