Windows: Replace AFSDbgMsgLog func with macro

In order to reduce computation overhead when trace logging is not
active replace the AFSDbgMsgLog function call with a macro,
AFSDbgTrace.

Change-Id: I7bccee0ddffcd8488f81fcebbb970aa15c8dc52e
Reviewed-on: http://gerrit.openafs.org/9621
Reviewed-by: Peter Scott <pscott@kerneldrivers.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>