Current implementation didn't honor quorum properly and didn't
handle the errors generated properly. This patch addresses that
and also moves common code `cleanupMultipartUploads` into xl
specific private function.
Fixes#3665
- Reads and writes of uploads.json in XL now uses quorum for
newMultipart, completeMultipart and abortMultipart operations.
- Each disk's `uploads.json` file is read and updated independently for
adding or removing an upload id from the file. Quorum is used to
decide if the high-level operation actually succeeded.
- Refactor FS code to simplify the flow, and fix a bug while reading
uploads.json.
Harshavardhana