Remove compiler warning on win32

Change-Id: I6c4697e5bae39f6c3438cc71acf0e1247f5a3708
Reviewed-on: http://review.couchbase.org/32307
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>