[audiopolicy][managerdefault] Filter unknown stream for volume settings

Stream for which no attributes is associated (aka no strategy supports it)
will use default attributes hence it will change the default strategy
volume (aka Music).
It leads to eroneous volume changes.
This bug does not happen on phone / tablets targets as all streams are
linked to a strategy with specifc attributes.
In case of OEM configuration, some stream types may not be supported
and associated to any strategy.

Test: dumpsys audio & dumpsus media.audio_policy.
    Ensure volumes of stream types and their aliases match.

Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: I5e12b2c7248074d10affb6c28d1866d4589cb9e8