fix incorrect OS condition

Change-Id: I3e5034bb0ce49f5aea297edbf989118905988a24
Reviewed-on: http://review.couchbase.org/33892
Tested-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>