remove dead code from ns_couchdb_api

Change-Id: Idc96bdad9810066cc7eeb1b32ccb50b9591f3430
Reviewed-on: http://review.couchbase.org/43816
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>