tests: add support for ospf instances with unified configs

[Jafaral]

No description provided.

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[mjstapp]

hmm - no description, and nothing in the commit comment, about what this is trying to do.
so ... was it not working to have the test script say "I want to run an ospf with this command-line arg, pointing at the unified config file?"
if we think we're going to drive daemon start and daemon command-lines from the config, then I think we need an explicit "daemon x" command for that purpose: there are too many things that may need to be expressed on the daemon command-line to try to do that implicitly.

[aceelindem]

I tried the tests/topotests/lib changes with 2 instances and this PR worked fine for me.

[Jafaral]

@mjstapp , sorry, this was a"quick" pr following a discussion on slack after @aceelindem raised the issue the he coudn't get ospf instances to work. This PR doesn't do anyting more/less than what is stated in the title.

1- This PR does NOT add support for unified config in the tests, that capability exists already
2- This PR does NOT remove the ability to configure or start individual daemons/instances
3- This PR doesn't mean multi instance isn't supported when using separate configs files.
4- This PR was added to configure ospf instances in topotests as an alternative method to using separate configs files, after some tests showed that the current support possibly does not work with more than one instance.

I'm mostly interested in using unified frr.conf, so:
Current behavior : If you choose to use frr.conf, and also configure ospf instances, it doesn't work
What this PR adds: support for ospf instances when using frr.conf unified configs

[Jafaral]

Also, I do agree that it is good to come up with a way to be able to pass commands arguments to a daemon when using unified configs. I like to solve that problem, but it is out of scope for this PR.

[riw777]

looks good

[riw777]

need to look at new core ...

[riw777]

rerunning failed test

[ton31337]

@Mergifyio backport stable/10.2

[mergify]

backport stable/10.2

✅ Backports have been created

• #17573 tests: add support for ospf instances with unified configs (backport #17331) has been created for branch stable/10.2 but encountered conflicts