rename some variables in rxperf

rename some variables in rxperf

sendtimes and recvtimes are actually the data byte counts to be
exchanged during an rpc test not an iteration count as implied
by their names

Reviewed-on: http://gerrit.openafs.org/2876
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 9d912b6f1c4f3d242429c66291107b2badd166e4)
Change-Id: Ie18184f5d6d911ba18ad216cb3726378333f6213
Reviewed-on: http://gerrit.openafs.org/3036