shutdown后报错：Expected state [STARTED] was [STOPPED]

- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.15
* Operating System version: mac
* Java version: 8

### Steps to reproduce this issue
环境：zk：3.6.0以上，curator：5.1.0以上

shutdown后，会报错：
```java
20:57:49.731 [main-EventThread] ERROR o.a.c.f.recipes.cache.NodeCache -
java.lang.IllegalStateException: Expected state [STARTED] was [STOPPED]
at org.apache.curator.shaded.com.google.common.base.Preconditions.checkState(Preconditions.java:823)
at org.apache.curator.framework.imps.CuratorFrameworkImpl.checkState(CuratorFrameworkImpl.java:457)
at org.apache.curator.framework.imps.CuratorFrameworkImpl.checkExists(CuratorFrameworkImpl.java:484)
at org.apache.curator.framework.recipes.cache.NodeCache.reset(NodeCache.java:261)
at org.apache.curator.framework.recipes.cache.NodeCache.access$100(NodeCache.java:60)
at org.apache.curator.framework.recipes.cache.NodeCache$2.process(NodeCache.java:104)
at org.apache.curator.framework.imps.NamespaceWatcher.process(NamespaceWatcher.java:77)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:588)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:563)
```

将zk降级到3.6.0以下就不会有这个问题，因为没框框里面这个事件。