datapath.go goes multi-bucket, multi-kvnode.

Change-Id: Ie8ac7c09f948a5e3fd81064ca58d75e6b60b7832
Reviewed-on: http://review.couchbase.org/39073
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>