Fix concurrent tests

Author: enricovianello

src/test/java/org/italiangrid/voms/test/mt/TestConcurrentValidation.java

@@ -179,7 +179,6 @@ public void test() throws InterruptedException, BrokenBarrierException {
       pool.execute(new ValidatorWorker());
 
     barrier.await();
-    barrier.await();
 
     pool.shutdown();
     sharedVOMSTrustStore.cancel();