Enable the sysv init scripts in OpenBSD build script

[hcartiaux]

Proposed Commit Message

<type>fix(openbsd)</type>: Enable sysv init scripts in OpenBSD build script

This replaces the use of `/etc/rc.local` in the OpenBSD build script by the sysv init scripts provided with cloud-init.

Fixes GH-4036
LP: #1992853

Additional Context

I've fixed a bug in the sysv init scripts by disabling rc_bg="YES", otherwise it would fail to execute correctly with this error at boot:

rcctl start cloudconfig 
cloudconfig/etc/rc.d/cloudconfig: kill: 66598: No such process
(ok)

Also, /etc/rc.local is not needed anymore, /var/run is managed by the system and does not have to be cleaned up manually.

Test Steps

My own CI: https://github.com/hcartiaux/openbsd-cloud-image/actions/

• Generate an OpenBSD 7.6 image with cloud-init 24.3.1
• Apply the diff with the post-install script install.site
• Generate a minimal iso with a ssh key
• Boot the previously generated image and wait until the VM is back

I've also tested manually to have a closer look at the output.

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[holmanb]

@igalic could you take a look at this please?