CBQE-0 :: fix failing start stop test cases : adjust to 6 nodes only

Change-Id: Ibe239aa613dfbc49a1019e49fe22bae7798bf194
Reviewed-on: http://review.couchbase.org/40040
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Parag Agarwal <agarwal.parag@gmail.com>
Tested-by: Parag Agarwal <agarwal.parag@gmail.com>