as of rails 4.0.4, touch fires after_commit callback - fixed test.

As of rails 4.0.4, touching a column will also fire the after_commit callback. rails changelog: <https://github.com/rails/rails/blob/v4.0.4/activerecord/CHANGELOG.md> ("Make touch fire the after_commit and after_rollback callbacks.") which means that one test is failing starting with rails 4.0.4.

In this pullrequest i just fixed the test, but I also want to raise the question: wouldn't it be better to work around using ```touch```, so that delete no longer raises the ```after_commit```callback? This would be nearer on the normal rails behaviour of having ```delete``` not firing any callbacks. As of now, ```delete``` also fires the ```after_touch``` callback, which might be surprising to some people.

 I'd be glad to look into it, if people think that's worth doing. Thanks for your feedback!