Issue 5044873: Pb with BT SCO AudioManager API

Do not identify the SCO connection client by the binder interface
passed when starting the connection as this binder changes if the
AudioManager proxy changes. Use the client PID instead.

This solves an issue with gTalk starting a SCO connection from one
AudioManager proxy and then changing audio mode from another thus
terminating the previously started SCO connection.

Change-Id: Ia3067fecc551fc15df3bf75ce0c43d181859e4f0