http/tests/xmlhttprequest/cross-origin-cookie-storage.html fails with PPT.

This test used to pass because some previous test leaked a cookie. Now that we
clear cookies between tests, it fails, and will fail until we implement testRunner.setAlwaysAcceptCookies.

* platform/mac-wk2/TestExpectations:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@175789 268f45cc-cd09-0410-ab3c-d52691b4dbfc