### Environment

* Dubbo version: 2.7.3
* Operating System version: CentOS7
* Java version: 1.8

### Steps to reproduce this issue

1. Set two protocal, with different "register" attribute

```xml
<dubbo:protocol name="dubbo" port="8751" register="true"  />
<dubbo:protocol name="hessian" port="8752" register="false" />
```

2. use the zookeeper registry center

```xml
<dubbo:registry address="..." file="./.dubbo_cache" />
```

3. start the server and view the provider in zkCli


### Expected Result
only the dubbo is registed

### Actual Result
the dubbo and hession protocol are registed

*
     * <li>when the url is dubbo://224.5.6.7:1234/org.apache.dubbo.config.api.DemoService?application=dubbo-sample, then
     * the protocol is <b>DubboProtocol</b></li>
     * <p>
     * Actually，when the {@link ExtensionLoader} init the {@link Protocol} instants,it will automatically wraps two
     * layers, and eventually will get a <b>ProtocolFilterWrapper</b> or <b>ProtocolListenerWrapper</b>
     */
    private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
    /**
     * A {@link ProxyFactory} implementation that will generate a exported service proxy,the JavassistProxyFactory is its
     * default implementation
     */
    private static final ProxyFactory PROXY_FACTORY = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
    /**
     * A random port cache, the different protocols who has no port specified have different random port
     */
    private static final Map<String, Integer> RANDOM_PORT_MAP = new HashMap<String, Integer>();
    /**
     * A delayed exposure service timer
     */
    private static final ScheduledExecutorService DELAY_EXPORT_EXECUTOR = Executors.newSingleThreadScheduledExecutor(new NamedThreadFactory("DubboServiceDelayExporter", true));
    /**
     * The urls of the services exported
     */
    private final List<URL> urls = new ArrayList<URL>();
    /**
     * The exported services
     */
    private final List<Exporter<?>> exporters = new ArrayList<Exporter<?>>();
    /**