remove unused function argument

Change-Id: I4431ab6843266896fa0dbe175c0213cc10bb37e2
Reviewed-on: http://review.couchbase.org/33705
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>