fixing String-based synchronization monitor issue, using Random string guaranteed to be unique per TrackedRaceImpl instance;

See also 4e3ad78640 where this problem had
been solved for another monitor object, also on TrackedRaceImpl

Change-Id: Ic6d9b1f7ed715f82198b7c3fa7b5398cbed4739d

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/TrackedRaceImpl.java

@@ -805,7 +805,7 @@ public abstract class TrackedRaceImpl extends TrackedRaceWithWindEssentials impl
     /**
      * Monitor object to synchronize access to the {@link #updateStartAndEndOfTracking(boolean)} method. See bug 3922.
      */
-    private final Serializable updateStartAndEndOfTrackingMonitor = "updateStartAndEndOfTrackingMonitor";
+    private final Serializable updateStartAndEndOfTrackingMonitor = ""+new Random().nextDouble();
     
     /**
      * Updates the start and end of tracking in the following precedence order: