修复 注册中心使用配置中心group属性的bug (#442)

diff --git a/dubbo-admin-server/src/main/java/org/apache/dubbo/admin/config/ConfigCenter.java b/dubbo-admin-server/src/main/java/org/apache/dubbo/admin/config/ConfigCenter.java
index 2879559..5682f9c 100644
--- a/dubbo-admin-server/src/main/java/org/apache/dubbo/admin/config/ConfigCenter.java
+++ b/dubbo-admin-server/src/main/java/org/apache/dubbo/admin/config/ConfigCenter.java
@@ -101,7 +101,7 @@
         }
         if (dynamicConfiguration == null) {
             if (StringUtils.isNotEmpty(registryAddress)) {
-                registryUrl = formUrl(registryAddress, configCenterGroup, username, password);
+                registryUrl = formUrl(registryAddress, registryGroup, username, password);
                 dynamicConfiguration = ExtensionLoader.getExtensionLoader(GovernanceConfiguration.class).getExtension(registryUrl.getProtocol());
                 dynamicConfiguration.setUrl(registryUrl);
                 dynamicConfiguration.init();