Register policy with AudioManager

The policy was previously not registered. Resulting in a failure when
starting the recording.

Test: atest android.media.cts.AudioPlaybackCaptureTest#testCaptureMediaUsage
Bug: 111453086
Change-Id: Ib0bbdfefd644c2f8e389baafdc1fc3ad548dcc4c
Signed-off-by: Kevin Rocard <krocard@google.com>