
### 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);
                }
                */
            }
        }
    };
```

*/
    protected boolean shouldJvmRefer(Map<String, String> map) {
        URL tmpUrl = new URL("temp", "localhost", 0, map);
        boolean isJvmRefer;
        if (isInjvm() == null) {
            // 
            if (url != null && url.length() > 0) {
                isJvmRefer = false;
            } else {
                // 
                isJvmRefer = InjvmProtocol.getInjvmProtocol().isInjvmRefer(tmpUrl);
            }
        } else {
            isJvmRefer = isInjvm();
        }
        return isJvmRefer;
    }
    /**
     * Dispatch an {@link Event event}
     *
     * @param event an {@link Event event}
     * @since 2.7.5
     */
    protected void dispatch(Event event) {
        EventDispatcher.getDefaultExtension().dispatch(event);
    }
    public DubboBootstrap getBootstrap() {
        return bootstrap;
    }
    public void setBootstrap(DubboBootstrap bootstrap) {