Windows: make osi_Log macro safe for if..else

Windows: make osi_Log macro safe for if..else

wrap the osi_Log macro's internal if statement with
a do {...} while(0) block in order to ensure that
it is safe for use in if..else controls without bracing.

Reviewed-on: http://gerrit.openafs.org/5189
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 6691ff6daceb7960dc925983a2b9129877e67c9a)

Change-Id: I954ea5a567bbfd77b02d3e8634a64f877668280e
Reviewed-on: http://gerrit.openafs.org/5211
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>