Fixes 'not win8 app' test for IE6/7

IE6/7 was barfing deleting the Mock window.Windows object we set up
for the prior 'win8 app' test, resulting in "Unexpected event error"
in the log, and since hte window.Windows Mock object stuck around,
'not win8 app' returned true, instead of false in IE6/7
Merge pull request #494 from sdesai/ua-win8app-test-fix

Fixes 'not win8 app' test for IE6/7