CBQE-791: Initialize nodes/buckets (sys tests)

- Options for bucket size

Change-Id: I08f1a03692734aa17816cda44f87ed5475700759
Reviewed-on: http://review.couchbase.org/24845
Reviewed-by: abhinav dangeti <abhinav.dangeti@gmail.com>
Tested-by: abhinav dangeti <abhinav.dangeti@gmail.com>