fix HTTP invalid host issue for channel not inited by http(s)

[thorneliu]

What problem does this PR solve?

Issue Number:
#1940

Problem Summary:
Invalid host in HTTP header if setting host via service_name for channel inited by list or file

What is changed and the side effects?

Changed:
check if ns_url shceme is 'http' or 'https', if true, set host field by service_name

Side effects:

• Performance effects(性能影响):
  NO impact
• Breaking backward compatibility(向后兼容性):
  NO impact

---

Check List:

• Please make sure your changes are compilable(请确保你的更改可以通过编译).
• When providing us with a new feature, it is best to add related tests(如果你向我们增加一个新的功能, 请添加相关测试).
• Please follow Contributor Covenant Code of Conduct.(请遵循贡献者准则).

[wwbmmm]

LGTM