Experiment with multiple kvnodes for datapath.

Change-Id: I4c258c18f60c2b8d525fd7782d0086d35b2f3bbf
Reviewed-on: http://review.couchbase.org/39013
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>