MB-10761: Include bucket/node in output csv file

In multi-bucket and/or multi-node  cluster environment, we cannot
use one csv file for output which leads to overwrite and data missing.
The final csv file format will be something like
<basename>_bucketname_nodename.csv

Change-Id: I05e970b60020c597cd24cf6320f1e32effdbad37
Reviewed-on: http://review.couchbase.org/36270
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>