modify unit test of producer

client/src/test/java/org/apache/rocketmq/client/producer/DefaultMQProducerTest.java

@@ -201,7 +201,7 @@ public class DefaultMQProducerTest {
             public void onException(Throwable e) {
             }
         });
-        countDownLatch.await(20000L, TimeUnit.MILLISECONDS);
+        countDownLatch.await(8000L, TimeUnit.MILLISECONDS);
         assertThat(cc.get()).isEqualTo(1);
     }