[sonos] Fix warnings (openhab#15708)

* Fix warnings
* Fix discovery error logging for offline devices

Fixes openhab#6793

Signed-off-by: Jacob Laursen <[email protected]>

Author: jlaur

bundles/org.openhab.binding.sonos/src/main/java/org/openhab/binding/sonos/internal/SonosAudioSink.java

@@ -22,7 +22,6 @@
 import org.openhab.binding.sonos.internal.handler.ZonePlayerHandler;
 import org.openhab.core.audio.AudioFormat;
 import org.openhab.core.audio.AudioHTTPServer;
-import org.openhab.core.audio.AudioSink;
 import org.openhab.core.audio.AudioSinkSync;
 import org.openhab.core.audio.AudioStream;
 import org.openhab.core.audio.FileAudioStream;
@@ -39,7 +38,7 @@
 import org.slf4j.LoggerFactory;
 
 /**
- * This makes a Sonos speaker to serve as an {@link AudioSink}-
+ * This makes a Sonos speaker to serve as an {@link org.openhab.core.audio.AudioSink}-
  *
  * @author Kai Kreuzer - Initial contribution and API
  * @author Christoph Weitkamp - Added getSupportedStreams() and UnsupportedAudioStreamException