MB-7626: tune rebalance options during cluster setup

Change-Id: Id9e69ccb2109f0c8cd331ccb0dfbc2afd0ca037c
Reviewed-on: http://review.couchbase.org/24581
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>