[Sheriff-o-matic] Remove race condition on the commit list.

Tools/GardeningServer/model/ct-commit-log-mock.html

 <!--
 Copyright 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <link rel='import' href='ct-commit-log.html'>
 
 <link rel='import' href='ct-commit-mock.html'>
 
 <script>
 (function () {
 
 window.CTCommitLogMock = function() {
   var repository = 'blink';
   var log = new CTCommitLog();
   var commit = new CTCommitMock();
-  log.commits[repository] = {};
   log.commits[repository][commit.revision] = commit;
   log._findFirstAndLastRevisions('blink')
   return log;
 };
 
 })();
 </script>