Leanback: Disable 9-patch shadow on API-19

There is a double applied delta issue in optical-bounds
causing a negative measured size.

Bug was fixed in API-20 and after:
https://googleplex-android-review.git.corp.google.com/#/c/431321/

Bug 30943877

Change-Id: I82f48f3c2b73884854691a4a67673a08ebed0594
1 file changed