Added getter for session Id to AudioSink

Added a method to expose the audio session id at AudioSink interface
so that the AudioPlayer in stagefright can retrieve it.

Also:
- Fixed audio effect send level not being initialized in mediaplayer.
- Fixed compilation error when LOGV is enabled in mediaplayer JNI

Change-Id: I4bb55454fd63d646e0e677692d737c4843fb05fb