Use hash stream instead of crypto.createHash

crypto.createHash is a write stream but not a PassThrough stream!

src/backupformat/rsync.js

@@ -19,6 +19,7 @@ const assert = require('assert'),
     debug = require('debug')('box:backupformat/rsync'),
     { EncryptStream } = require('../hush.js'),
     fs = require('fs'),
+    HashStream = require('../hash-stream.js'),
     hush = require('../hush.js'),
     path = require('path'),
     paths = require('../paths.js'),
@@ -52,7 +53,7 @@ async function addFile(sourceFile, encryption, uploader, progressCallback) {
         progressCallback({ message: `Uploading ${sourceFile}: ${transferred}M@${speed}MBps` }); // 0M@0MBps looks wrong
     });
 
-    const hash = crypto.createHash('sha256');
+    const hash = new HashStream();
 
     let pipeline = null;
     if (encryption) {