fix #1957

DefaultMQProducer didn't shutdown completely

client/src/main/java/org/apache/rocketmq/client/impl/factory/MQClientInstance.java

@@ -853,6 +853,7 @@ public class MQClientInstance {
                     this.scheduledExecutorService.shutdown();
                     this.mQClientAPIImpl.shutdown();
                     this.rebalanceService.shutdown();
+                    this.defaultMQProducer.shutdown();
 
                     if (this.datagramSocket != null) {
                         this.datagramSocket.close();

client/src/main/java/org/apache/rocketmq/client/impl/producer/DefaultMQProducerImpl.java

@@ -258,7 +258,7 @@ public class DefaultMQProducerImpl implements MQProducerInner {
                 if (shutdownFactory) {
                     this.mQClientFactory.shutdown();
                 }
-
+                this.timer.cancel();
                 log.info("the producer [{}] shutdown OK", this.defaultMQProducer.getProducerGroup());
                 this.serviceState = ServiceState.SHUTDOWN_ALREADY;
                 break;