mixer: update internal volume and call the changed event
mixer: update internal volume and call the changed event

tizenorg/platform.upstream.enlightenment,rvandegrift/e,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,rvandegrift/e,rvandegrift/e,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,tasn/enlightenment