Audio HAL VTS: Allow OK when setting a non existing parameter

setHwAvSync and setParameters were implemented in the pre-hidl interface
as set_parameters.
Unfortunately set_parameters did not return an error if a key was not
implemented.

As most HIDL implementation will be a wrapper around the pre-hidl
interface, allow those functions to return OK on not implemented key.

Test: vts-tradefed run vts --module VtsHalAudioV2_0Target
Test: call/play music/record/video...
Bug: 36311550
Change-Id: Icfcaa02b7d63e03375fddc90dc5a803754c1874f
Signed-off-by: Kevin Rocard <krocard@google.com>