fix #1352 DatePickerWithValidatorTest IE7 failure

This fixes a new test added in 7b13250738d1f2a58bd98ce2ae55d558648d4134
which was found to be failing in IE7 during release testing.

The test was failing in IE7 due to IE7 being served a different HTML
than other browsers (one more nested span in IE7). New test checks
still different HTML elements in IE7 and non-IE7 browsers, though both
of them should have an error CSS class.