
### Environment

* Dubbo version: 2.7.4.1

### Steps to reproduce this issue

在dubbo正常启动的时候，会出现很多一样的警告
```
2020-03-11 22:56:34.344 [Finalizer] [WARN] com.alibaba.dubbo.config.AbstractConfig -  [DUBBO] ReferenceConfig(null) is not DESTROYED when FINALIZE, dubbo version: 2.6.4, current host: 192.168.31.245
2020-03-11 22:56:34.345 [Finalizer] [WARN] com.alibaba.dubbo.config.AbstractConfig -  [DUBBO] ReferenceConfig(null) is not DESTROYED when FINALIZE, dubbo version: 2.6.4, current host: 192.168.31.245
2020-03-11 22:56:34.345 [Finalizer] [WARN] com.alibaba.dubbo.config.AbstractConfig -  [DUBBO] ReferenceConfig(null) is not DESTROYED when FINALIZE, dubbo version: 2.6.4, current host: 192.168.31.245
```
是从下面触发了finalize()方法发出，但是现在这个里面也已经没有做任何操作了，是不是可以把finalizerGuardian去掉了？
```
 private final Object finalizerGuardian = new Object() {
        @Override
        protected void finalize() throws Throwable {
            super.finalize();

            if (!ReferenceConfig.this.destroyed) {
                logger.warn("ReferenceConfig(" + url + ") is not DESTROYED when FINALIZE");

                /* don't destroy for now
                try {
                    ReferenceConfig.this.destroy();
                } catch (Throwable t) {
                        logger.warn("Unexpected err when destroy invoker of ReferenceConfig(" + url + ") in finalize method!", t);
                }
                */
            }
        }
    };
```

this.bootstrap = bootstrap;
    }
    @SuppressWarnings("unused")
    private final Object finalizerGuardian = new Object() {
        @Override
        protected void finalize() throws Throwable {
            super.finalize();
            if (!ReferenceConfig.this.destroyed) {
                logger.warn("ReferenceConfig(" + url + ") is not DESTROYED when FINALIZE");
                /* don't destroy for now
                try {
                    ReferenceConfig.this.destroy();
                } catch (Throwable t) {
                        logger.warn("Unexpected err when destroy invoker of ReferenceConfig(" + url + ") in finalize method!", t);
                }
                */
            }
        }
    };
    private void postProcessConfig() {
        List<ConfigPostProcessor> configPostProcessors =ExtensionLoader.getExtensionLoader(ConfigPostProcessor.class)
                .getActivateExtension(URL.valueOf("configPostProcessor://"), (String[]) null);
        configPostProcessors.forEach(component -> component.postProcessReferConfig(this));
    }
    // 
    Invoker<?> getInvoker() {
        return invoker;
    }
}