DUBBO-456 去掉不必要的参数

dubbo-registry/dubbo-registry-api/src/main/java/com/alibaba/dubbo/registry/support/AbstractRegistryFactory.java

@@ -80,7 +80,9 @@ public abstract class AbstractRegistryFactory implements RegistryFactory {
     }
 
     public Registry getRegistry(URL url) {
-    	url = url.setPath(RegistryService.class.getName()).addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName());
+    	url = url.setPath(RegistryService.class.getName())
+    			.addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName())
+    			.removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY);
     	String key = url.toServiceString();
         // 锁定注册中心获取过程，保证注册中心单一实例
         LOCK.lock();