Fixup warnings under -Werror -Wextra

Change-Id: Ia6994fa85251549b441f31b742542a11a106e4ef
Reviewed-on: http://review.couchbase.org/29599
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Volker Mische <volker.mische@gmail.com>