Add transport information for debugging, gathering data and other purposes

Hi, as we know, we can use pool to go around the servers. I'm trying to log and monitor the response from ES and want to get which server serves my request, how long does it takes. Those information is only in $response['info'] from transport object but we return only data.

So my patch is about adding connection information to $response['data'] then we can get it for debugging, gathering data and other purposes.