Changes done for disconnecting sco connection based on disconnectAudioNative()...

Changes done for disconnecting sco connection based on disconnectAudioNative() return status, instead of waiting till BTA_AG_AUDIO_CLOSE_EVT is received. The delay in disconnecting sco was causing audio to be routed to earpiece instead of speaker, when selected from incall screen.

Change-Id: I307c3e9c114676649750cb64f1043fc7fe79d71b