audio policy service: filter out delayed audio patch commands if needed.

As for set parameters commands, create or release audio patch commands
modifying the same patch handle should be filtered by the audio policy service
command thread so that an immediate command is not overridden by
a pending delayed command.

Bug: 17379728.

Change-Id: I6aa4652b4bfec59eebd3c3cb7d1d9ac1bc1d6e49