Remove XL multipart tmp files when the latter is canceled (#3214)

XL multipart fails to remove tmp files when an error occurs during upload, this case covers the scenario where an upload is canceled manually by the client in the middle of job.

cmd/posix.go

@@ -944,5 +944,11 @@ func (s *posix) RenameFile(srcVolume, srcPath, dstVolume, dstPath string) (err e
 		}
 		return err
 	}
+
+	// Remove parent dir of the source file if empty
+	if parentDir := slashpath.Dir(preparePath(srcFilePath)); isDirEmpty(parentDir) {
+		deleteFile(srcVolumeDir, parentDir)
+	}
+
 	return nil
 }