[ISSUE #3066]producing a ghost consumer

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

@@ -863,7 +863,7 @@ public class MQClientInstance {
         }
     }
 
-    public boolean registerConsumer(final String group, final MQConsumerInner consumer) {
+    public synchronized boolean registerConsumer(final String group, final MQConsumerInner consumer) {
         if (null == group || null == consumer) {
             return false;
         }
@@ -877,9 +877,9 @@ public class MQClientInstance {
         return true;
     }
 
-    public void unregisterConsumer(final String group) {
+    public synchronized void unregisterConsumer(final String group) {
         this.consumerTable.remove(group);
-        this.unregisterClientWithLock(null, group);
+        this.unregisterClient(null, group);
     }
 
     private void unregisterClientWithLock(final String producerGroup, final String consumerGroup) {