MediaFocusControl: Fix audio focus logic

This fixes commit 007e15d5d.

Should have been checking for when the notification stream is 0, not non-zero.

Change-Id: Idde589064082875d13a342445bb2b9de6b41e872
Signed-off-by: Evan Anderson <evan1124@gmail.com>
[1/2]Base: Stylus Gestures

Change-Id: I35f5b9128ffff4df87c160e27cf86624ed6333e7