backuptask: track copy and upload statistics

src/backupformat/tgz.js

@@ -170,12 +170,12 @@ async function tarPack(dataLayout, encryption, uploader, progressCallback) {
     const [error] = await pipeline; // already wrapped in safe()
     if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `tarPack pipeline error: ${error.message}`);
 
-    const stats = ps.stats();
+    const stats = ps.stats(); // { startTime, totalMsecs, transferred }
     debug(`tarPack: pipeline finished: ${JSON.stringify(stats)}`);
 
     await uploader.finish();
     return {
-        stats: { fileCount, size: stats.transferred, ...stats },
+        stats: { fileCount, size: stats.transferred, transferred: stats.transferred },
         integrity: { size: stats.transferred, fileCount, sha256: hash.digest('hex') }
     };
 }