Refactor newProducer() functions to match passed params

Change-Id: Ia5b4828a969ec204469ad03ae25caad2adb8d33c
Reviewed-on: http://review.couchbase.org/30027
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>