Audio HAL VTS: Some methods are optional

Although the method documentation does not say it,
some HIDL interface methods are optional.

Update the tests to allow NOT_SUPPORTED to be returned.

Test: vts-tradefed run vts --module VtsHalAudioV2_0Target
Test: call/play music/record/video...
Bug: 36311550
Change-Id: If31acc2dbdb6d1d563910e85c99401c48f4f3f86
Signed-off-by: Kevin Rocard <krocard@google.com>