Make openrc override command logic generic for other services besides k3s

[mauromorales]

The openrc override command is done via the following function

https://github.com/kairos-io/kairos-sdk/blob/c21aa7f149cbbea5416f7fd475d9c6613d208d4e/machine/openrc/unit.go#L62

Unfortunately, this is too k3s specific, the command should work for any other service.