audio policy: fix enforced audible playback

When selecting device on a given output stream, check if
an enforced audible sound is active on any other output stream and
not just on this stream.

Bug: 124063442
Test: set property audio.camerasound.force=true and test music + shutter
sound concurrency.

Change-Id: Ic7f548df2b67041d532afc68685cdbeb3cb3f125