* fix/TD-20817-mac-fqdn use localhostname

* fix/TD-20817-mac-fqdn redundant codes

* fix/TD-20817-mac-fqdn,replace command with api
Co-authored-by: Nfacetosea <25808407@qq.com>
Co-authored-by: Shuduo Sang <sangshuduo@gmail.com>