fix(rngd): install system service file

[pvalena]

Note: this is dependent Fedora / RH rngd service file containing

ExecStart=/usr/sbin/rngd -f $RNGD_ARGS

Changes

Use system service file, but ship modified args to drop the user change.
There's no reason to keep a copy of rngd.service; there shouldn't be any modifications.

In case there are args stored in a separate file (Fedora and alike), it needs to be supplied too, but without the option to change the user.

Checklist

• I have tested it locally
• I have reviewed and updated any documentation if relevant
• I am providing new code and test(s) for it

[LaszloGombos]

For reference - earlier discussion on this - dracutdevs/dracut#2442

[LaszloGombos]

This PR in its current form breaks FULL-SYSTEMD test on Arch.

rngd.service in Arch

CC @freswa @dalto8

[freswa]

Is it correct, that the test is only failing due to the different ENV var naming?

[LaszloGombos]

https://bugzilla.redhat.com/show_bug.cgi?id=2181540

[pvalena]

https://bugzilla.redhat.com/show_bug.cgi?id=2181540

Yeah, that was why I created this. To not update it / ship it further in the future. Sorry, I lost the reference - but will put it into the commit msg.

[pvalena]

Is it correct, that the test is only failing due to the different ENV var naming?

@freswa Yes, I think so - RNGD_OPTS vs RNGD_ARGS. I can add both into sysconfig file though, if you're against renaming the ENV.

[freswa]

Is it correct, that the test is only failing due to the different ENV var naming?

@freswa Yes, I think so - RNGD_OPTS vs RNGD_ARGS. I can add both into sysconfig file though, if you're against renaming the ENV.

Not at all. I think we're ok renaming it.