feat: 优化systemctl中判断service文件是否存在的函数

[igophper]

What this PR does / why we need it?

我发现在我的机器上，当点击主机->进程守护时，页面加载并不是很快，需要等待3秒左右的服务器返回时间，因为调用了systemctl 判断service文件是否存在的函数导致的。我想要减少等待。SSH管理的配置加载也因为这个需要等待1秒左右。优化后在我的机器上等待时间变为了毫秒。

Summary of your change

优化systemctl中判断service文件是否存在的函数
将原先列出文件的命令list-unit-files改为is-enabled进行判断

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

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[wanghe-fit2cloud]

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