testrunner: Putting back the global variables used for ajax tests. I added many calls to delete though. The global namespace must be cleaned up before calling start() again.

test/data/test.js

@@ -1,3 +1,3 @@
-jQuery.foobar = "bar";
+foobar = "bar";
 jQuery('#ap').html('bar');
 ok( true, "test.js executed");