Adapt to goforestdb API changes.

Change-Id: I31c1a0cf0d5cad2fb7d4134d056d63197771c90b
Reviewed-on: http://review.couchbase.org/42940
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>