Remove compiler warnings

Change-Id: I48743038fba8bb9df4a8d392b48bd79d8029a16d
Reviewed-on: http://review.couchbase.org/30703
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>