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

### Environment

* Dubbo version: 2.7.3
* Operating System version: Mac OS
* Java version: 1.8

### Steps to reproduce this issue

1.RouterChain#buildChain(URL)
2.RouterChain#initWithRouters()
3.RouterChain#sort()


### Expected Result

ServiceRouter is High priority than AppRouter

### Actual Result

AppRouter is High priority than ServiceRouter

### Cause by
the code was on ListenableRouter 94~96 line
```
public abstract class ListenableRouter extends AbstractRouter implements ConfigurationListener {    
    ......
    ......
    @Override
    public int getPriority() {
        return DEFAULT_PRIORITY;
    }
```
### Resolve
i think can like this：
```
public abstract class ListenableRouter extends AbstractRouter implements ConfigurationListener {    
    ......
    ......
    @Override
    public int getPriority() {
        return priority;
    }
```
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package org.apache.dubbo.rpc.cluster.router.condition.config;
import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.config.configcenter.ConfigChangeType;
import org.apache.dubbo.common.config.configcenter.ConfigChangedEvent;
import org.apache.dubbo.common.config.configcenter.ConfigurationListener;
import org.apache.dubbo.common.config.configcenter.DynamicConfiguration;
import org.apache.dubbo.common.logger.Logger;