Windows: use local var for interlocked result

Windows: use local var for interlocked result

Save the result of the interlocked operations for use in
debug logging.  Do not reference the incremented or decremented
object in the log messages, it may have changed.

Local assignment is provided even in functions that are currently
not logging to assist with debugging and as a reminder to use
the result variable in future log messages.

Change-Id: Ia7ed8bf14b204b265e1db7713b96864634a731d7
Reviewed-on: http://gerrit.openafs.org/6508
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>