修复重复拉取未读消息的bug

im-platform/src/main/java/com/bx/implatform/task/PullAlreadyReadMessageTask.java

@@ -64,7 +64,7 @@ public class PullAlreadyReadMessageTask {
                 Thread.sleep(200);
             }finally {
                 // 下一次循环
-                if(executorService.isShutdown()){
+                if(!executorService.isShutdown()){
                     executorService.submit(this);
                 }
             }