Changed number of threads in executerservice to one to prevent false order to save file

app/src/main/java/ch/zhaw/projekt2/turnierverwaltung/TournamentDecorator.java

@@ -27,7 +27,7 @@ public class TournamentDecorator implements IsObservable{
                 }
             }
         });
-        executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
+        executorService = Executors.newFixedThreadPool(1);
     }
 
     public void setFactoryDecorator(FactoryDecorator factoryDecorator) {