Environment

• Dubbo version: latest version
• Operating System version: LINUX & WINDOWS
• Java version: 1.8

Steps to reproduce this issue

必现哦

Pls. provide [GitHub address] to reproduce this issue.

Expected Result

VERSION_KEY和GROUP_KEY为空时，注册到NACOS的服务名不带双冒号后缀。

Actual Result

What actually happens?

VERSION_KEY和GROUP_KEY为空时，注册到NACOS的服务名有双冒号后缀，与alibaba实现不一致。
alibaba实现是为空时无双冒号后缀。