Response format: 8001/clusters?format=json doesn't support json response encoding

Description:

Nope, just curl a request against 8001/clusters?format=json doesn't support json response encoding.

Repro steps:

curl "http://:8001/clusters?format=json

Returns just a list of metric/value pairs.