opensl: keep recording if no buffer available

src/media/audio/opensl/audio_player.cpp

src/media/audio/opensl/audio_recorder.cpp

src/media/audio/opensl/audio_recorder.h

src/media/audio/opensl/buf_manager.h

src/media/audio/opensl/opensllayer.cpp

src/media/audio/opensl/opensllayer.h