* Disable Nagle at the end of error messages so they are sent before
the socket is closed.
* Correctly discard file contents when the PUT file is too large.
* Correctly reset file size after failure to setting it too large.
* Change diskinfo.json to be list of disks in preparation of supporting
multiple disks.
* Bump version to 3 for the above change.
* Document diskinfo.json.
Fixes#8109
8208ca3c6f