Audio HAL VTS: differentiate getParam success/failure/not_implemented

When sending parameters to the HAL (and some getters are implemented
with getParameters), the client expect a status consistent
with the other HIDL methods. Ie: not implemented or success and failure.

Unfortunately, the legacy get_parameter interface, which currently most
Audio HIDL implementation are a wrapper around, do not return such error
code.

Get parameters return a list of key values.
 - If a requested key does not return a key value pair, consider it not
   implemented
 - If a requested key returns a key not followed by a correct value,
   consider it a failure
 - otherwise it is a success

Test: vts-tradefed run vts --module VtsHalAudioV2_0Target
Test: call/play music/record/video...
Bug: 36311550
Change-Id: Id6711e9c1974fe5a336b6de83a9b6d14f74437c9
Signed-off-by: Kevin Rocard <krocard@google.com>