Why does not tomcat throw an exception when `server.start` failed with a socket binding error.

https://github.com/apache/incubator-dubbo/blob/master/dubbo-remoting/dubbo-remoting-http/src/main/java/org/apache/dubbo/remoting/http/tomcat/TomcatHttpServer.java#L71

I do see the exception stack printed on the Console, whereas no exception was thrown in here:
```java
try {
            tomcat.start();
        } catch (LifecycleException e) {
            throw new IllegalStateException("Failed to start tomcat server at " + url.getAddress(), e);
        } catch (Exception ee) {
            throw new IllegalStateException(e);
        }

```

This behavior will cause a tomcat based HTTP service being registered unexpectedly to the Registry even after the binding has failed.

```java
@Override
    public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
         ... ...
        // socket binding exception extected
        final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);
        ... ... 
        // url to registry
        final Registry registry = getRegistry(originInvoker);
        register(registryUrl, registeredProviderUrl);
         
        return new DestroyableExporter<>(exporter);
    }
```
tomcat.getConnector().setProperty(
                "maxThreads", String.valueOf(url.getParameter(Constants.THREADS_KEY, Constants.DEFAULT_THREADS)));
        tomcat.getConnector().setProperty(
                "maxConnections", String.valueOf(url.getParameter(Constants.ACCEPTS_KEY, -1)));
        tomcat.getConnector().setProperty("URIEncoding", "UTF-8");
        tomcat.getConnector().setProperty("connectionTimeout", "60000");
        tomcat.getConnector().setProperty("maxKeepAliveRequests", "-1");
        tomcat.getConnector().setProtocol("org.apache.coyote.http11.Http11NioProtocol");
        Context context = tomcat.addContext("/", baseDir);
        Tomcat.addServlet(context, "dispatcher", new DispatcherServlet());
        context.addServletMapping("/*", "dispatcher");
        ServletManager.getInstance().addServletContext(url.getPort(), context.getServletContext());
        try {
            tomcat.start();
        } catch (LifecycleException e) {
            throw new IllegalStateException("Failed to start tomcat server at " + url.getAddress(), e);
        }
    }
    @Override
    public void close() {
        super.close();
        ServletManager.getInstance().removeServletContext(url.getPort());
        try {
            tomcat.stop();
        } catch (Exception e) {
            logger.warn(e.getMessage(), e);
        }
    }
}