MB-11820: Check if bucket is ready before populating data

Also, leverage cbtransfer to upload json files to cluster

Change-Id: Ia9071874826c45443f75d275b374496cba217028
Reviewed-on: http://review.couchbase.org/40660
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>