Update the scale on corner radii on scaled image drawable.

The RoundedDrawableWrapper applies rounded corners on each draw, so,
on scaling, the corners look odd for small widgets.

This change, applies the same scale to corner radius as well.
There are some widgets whose preview images have embedded transparency,
but we don't do much for such previews.

Bug: 359860747
Test: Manual
Flag: EXEMPT bugfix
Change-Id: I5e58e29765503454f286d99050b13b497531d306