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

### Environment

* Dubbo version: 2.6.4

### Steps to reproduce this issue

1. GenericService泛化调用
2. 使用oninvoke、onreturn、onthrow
3. FutureFilter无法正常回调

### Expected Result
StaticContext.getKey(invoker.getUrl(), invocation.getMethodName(), Constants.ON_INVOKE_METHOD_KEY)
返回
com.alibaba.boot.dubbo.demo.consumer.DemoService:1.0.0.sayHello.oninvoke.method

### Actual Result
StaticContext.getKey(invoker.getUrl(), invocation.getMethodName(), Constants.ON_INVOKE_METHOD_KEY)
返回
com.alibaba.boot.dubbo.demo.consumer.DemoService:1.0.0.$invoke.oninvoke.method

预期是：

```
        String methodName = invocation.getMethodName();
        if("$invoke".equals(methodName)) {
            Object[] arguments = invocation.getArguments();
            methodName = (String) arguments[0];
        }
```

*/
    private static final Protocol refprotocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
    /**
     * The {@link Cluster}'s implementation with adaptive functionality, and actually it will get a {@link Cluster}'s
     * specific implementation who is wrapped with <b>MockClusterInvoker</b>
     */
    private static final Cluster cluster = ExtensionLoader.getExtensionLoader(Cluster.class).getAdaptiveExtension();
    /**
     * A {@link ProxyFactory} implementation that will generate a reference service's proxy,the JavassistProxyFactory is
     * its default implementation
     */
    private static final ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
    /**
     * The url of the reference service
     */
    private final List<URL> urls = new ArrayList<URL>();
    /**
     * The interface name of the reference service
     */
    private String interfaceName;
    /**
     * The interface class of the reference service
     */
    private Class<?> interfaceClass;
    
    /**
     * client type
     */
    private String client;
    /**