added script to validate vbmap rack awareness constraint

Change-Id: I17808d0e92470ee610ca4503b65e5059580f381f
Reviewed-on: http://review.couchbase.org/30854
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>