List buckets (unfortunately) doesn't use multipart for the stream, it uses the same pattern as the streaming list-keys. e.g.:

```
$ curl localhost:8098/buckets?buckets=stream
{"buckets":["kyhkteliottt","ewwxnaqjqppf"]}{"buckets":["zsanvwyqammz","qqyidupkfidl","qfzjhnwbsofm","eltqprfopxcc"]}{"buckets":["ckrshatgcjaj","boctymxiycdl","2itest"]}{"buckets":["ytytqcnmqhii","iipguceptxhp"]}{"buckets":["phduuejisilx"]}{"buckets":["xpwiuiydiszs","wvtxijapplzv","hifefytfsifg"]}{"buckets":["hhvlovzznipr"]}{"buckets":["fcploumgzpnv"]}{"buckets":["fejmohhpqtay","amvkhqrbdjxi"]}{"buckets":["finfvbfgbata"]}{"buckets":["ucrtohfnmeia"]}{"buckets":["wsmmaygbgbli","lexgnrqqajbs","jnhgnipaqwee"]}{"buckets":["utborjesfker"]}{"buckets":[]}
```