audiopolicy: allow to identify internal strategies by attributes

A unique tag is given to internal strategies to prevent confusion with
default strategy, overwritting volume or mute attribute of these internal
strategies.

Test: make
Bug: 179759299
Bug: 249966139
Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: I3c08ca3f5445a2da02b25be0e008aa95e46d4289