Fixing radius of notification focus overlay

Focus overlay doesn't fully cover corners of notification background it's is peeking from beneath.
It's caused by using stroke instead of filling with color - notification background drawable is layer drawable
with all shapes being the same but when shape (as Path object) is drawn using stroke, stroke is centered on the path.
That means drawable is bigger by stroke width / 2 and when it's fitted inside NotificationBackgroundView it needs to be scaled down.
That changes radius shape and radius needs to be decreased to account for that.

Fixes: 329250144
Flag: None
Test: focus on notification and see notification background corners are not going outside of focus overaly
Change-Id: Ib8948bc9559bf2598af63185bcd14f073e39bfa7