audiopolicy: Defer release of output session effects

 * Some effects modules are racy and don't tolerate being destroyed
   and immediately resurrected on the same session. This is
   the common case when switching tracks, and the use of default
   output effects makes the problem even worse. Certain apps
   which handle gapless in a sloppy way are also to blame.
 * Instead of immediately nuking the entire descriptor with the
   stream, just decrease the refcount and defer it for 10 seconds.
   If it needs resurrected, the refcount will be increased and
   the delayed release command will not shoot it in the face.

Change-Id: I068dd72c4180023a74eb9ccbe8a180f6f0683dbf