scrollview: Ignore Scrollbars test on Android 4.4+

This test is a known failure on Android 4.4.x, due to how Chrome for Android now adds additional padding pixels to the ScrollView's `boundingBox`.

This doesn't affect the general use case, though this test and the one above it should likely be refactored.

@rgrove - let me know if you think that this might be a blocker for tomorrow and shouldn't be ignored.