Audio HAL VTS: Sanitize setMode input

Some values of AudioMode are exposed although implementation detail.
Make sure the client can not use them.

Test: vts-tradefed run vts --module VtsHalAudioV2_0Target
Test: call/play music/record/video...
Bug: 36311550
Change-Id: If513c2a06efa8a92459f0af80c63232fc63302b0
Signed-off-by: Kevin Rocard <krocard@google.com>