Modify ACodec to allow using Treble.

ACodec will connect to the Treble version of Omx if the property
"debug.treble_omx" is set to true ("1", "y", "yes", "true" or "on").

Also, fix some bugs found so far.

Test: Compiles
Bug: 31399200
Change-Id: I52b27b5f99bc1d6797d3b83b8be794ed2de9956a