Windows: PerformanceTuningInterval Merge error

Windows: PerformanceTuningInterval Merge error

Due to a merge error, if RankServerInterval was set via the
registry, its value would also be used for the
PerformanceTuningInterval.  Fix it.

Reviewed-on: http://gerrit.openafs.org/3500
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 6229ffb7ae365174ccacabe00d1e986d2f9b2019)

Change-Id: I7ed0ffbffc88c25e6b586d927c8422711d2bd7b8
Reviewed-on: http://gerrit.openafs.org/3800
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>