duplicate json key "echoParams" should be removed in ping-response

Apparently the /admin/ping handler will duplicate the echoParams key in the json-response.

$ curl -s http://localhost:8983/solr/test-node-client/admin/ping?wt=json
{"responseHeader":{"status":0,"QTime":2,"params":{"df":"text","echoParams":"all","rows":"10","echoParams":"all","wt":"json","q":"solrpingquery","distrib":"false"}},"status":"OK"}

Having "echoParams":"all" twice in that response doesn't really make sense?

Strictly speaking this is allowed in the json spec, so it is not a violation in principle
http://stackoverflow.com/questions/21832701/does-json-syntax-allow-duplicate-keys-in-an-object

However there are some json-parse implementations out there that want to map this into hashtables and are not silently overwriting the key with the last seen value, but are throwing errors in the process.

To those a cleanup of the json response would make life somewhat easier.