audiopolicy: allows to fallback or not on default strategy/group

When attributes does not match a group or strategy, it falls back on
respectively default group or strategy.

This CL allows to control whether fallback shall be done or not.
It allows for example to detect orphans attributes and prevent from
overwritting volume for example.

Bug: 179759299
Test: make

Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: Ieeeab48ca3ec2b031b7a99e2e7ab26d2e4d70535