return fix runnable.run() method call

src/main/java/org/codelibs/fess/mylasta/direction/sponsor/FessMailDeliveryDepartmentCreator.java

@@ -120,8 +120,7 @@ public class FessMailDeliveryDepartmentCreator {
         asyncManager.async(new ConcurrentAsyncCall() {
             @Override
             public void callback() {
-                Thread thrd = new Thread(runnable);
-                thrd.start();
+                runnable.run();
             }
 
             @Override