[AudioPolicy][engine][Strategy] fallback on music stream

If a strategy matches a attributes, whatever a stream type has
been provided, the MUSIC stream type shall be returned as a fallback
to ensure AudioFlinger will apply the right gain to the right stream
(which always fallback as music if none is provided)

Test: build & run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioProductStrategyTest
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioVolumeGroupTest
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioVolumeGroupChangeHandlerTest
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioManagerTest#testPermissionsForVolumePerAttributes
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioManagerTest#testGetAndValidateProductStrategies
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioManagerTest#testGetAndValidateVolumeGroups
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioManagerTest#testSetGetVolumePerAttributesWithInvalidAttributes
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioManagerTest#testSetGetVolumePerAttributes
run cts-dev -m CtsMediaTestCase --test android.media.cts.AudioManagerTest#testVolumeGroupCallback

Signed-off-by: François Gaffie <francois.gaffie@renault.com>
Change-Id: Ic79effb1341b788d90f5d73d23ae92b983f17225