ListMultipartUploads, ListObjectParts return empty response (#4694)

Also, periodically removes incomplete multipart uploads older than 2 weeks.

cmd/fs-v1.go

@@ -157,6 +157,9 @@ func newFSObjectLayer(fsPath string) (ObjectLayer, error) {
 		return nil, fmt.Errorf("Unable to initialize event notification. %s", err)
 	}
 
+	// Start background process to cleanup old files in minio.sys.tmp
+	go fs.cleanupStaleMultipartUploads()
+
 	// Return successfully initialized object layer.
 	return fs, nil
 }