Always play "sonar" on call initialization

If "sonar" was the last sound played on the last call, it wasn't
 being played on the next calling attempt.

Closes #4473

src/org/thoughtcrime/redphone/audio/OutgoingRinger.java

@@ -116,6 +116,7 @@ public class OutgoingRinger implements MediaPlayer.OnCompletionListener, MediaPl
       mediaPlayer.stop();
     } catch( IllegalStateException e ) {
     }
+    currentSoundID = -1;
   }
 
   private void stop( int soundID ) {