juju scp fails when control-plane doesn't have a public ip

[Bas de Bruijne]

In testrun https://solutions.qa.canonical.com/v2/testruns/433b51ed-0b88-41e4-a908-9cdfbca65d88, which is ck8s 1.26 focal on openstack, test_audit_custom_policy fails with:

```
2023-02-17-01:38:45 root DEBUG =================================== FAILURES ===================================
2023-02-17-01:38:45 root DEBUG ___________________________ test_audit_custom_policy ___________________________
2023-02-17-01:38:45 root DEBUG Traceback (most recent call last):
2023-02-17-01:38:45 root DEBUG File "/home/ubuntu/k8s-validation/jobs/integration/validation.py", line 1260, in test_audit_custom_policy
2023-02-17-01:38:45 root DEBUG await scp_to(f.name, unit, path, tools.controller_name, tools.connection)
2023-02-17-01:38:45 root DEBUG File "/home/ubuntu/k8s-validation/jobs/integration/utils.py", line 196, in scp_to
2023-02-17-01:38:45 root DEBUG await asyncify(subprocess.check_call)(cmd.split())
2023-02-17-01:38:45 root DEBUG File "/home/ubuntu/k8s-validation/jobs/integration/utils.py", line 104, in wrapper
2023-02-17-01:38:45 root DEBUG return await loop.run_in_executor(None, partial)
2023-02-17-01:38:45 root DEBUG File "/usr/lib/python3.8/concurrent/futures/thread.py", line 57, in run
2023-02-17-01:38:45 root DEBUG result = self.fn(*self.args, **self.kwargs)
2023-02-17-01:38:45 root DEBUG File "/usr/lib/python3.8/subprocess.py", line 364, in check_call
2023-02-17-01:38:45 root DEBUG raise CalledProcessError(retcode, cmd)
2023-02-17-01:38:45 root DEBUG subprocess.CalledProcessError: Command '['juju', 'scp', '-m', 'foundation-openstack:admin/kubernetes-openstack', '/home/ubuntu/.local/share/juju/tmpyhg_am35/tmpq7mlaepb', 'kubernetes-control-plane/0:/tmp/validate_audit_custom_policy-namespace.yaml']' returned non-zero exit status 1.
```

The reason is that since recently, we are not giving k8c-cp a public IP when deployed on OpenStack, which means that `juju scp` does not work.

[George Kraft (cynerva)]

PR: https://github.com/charmed-kubernetes/jenkins/pull/1213

This adds a --juju-ssh-proxy option to the validation suite that will proxy Juju SSH/SCP commands through the Juju controller. You will need to pass the new option in to the validation suite, but hopefully this does the trick.

[Canonical Solutions QA Bot (oil-ci-bot)]

This bug is fixed with commit 4320902a to cpe-foundation on branch master.
To view that commit see the following URL:
https://git.launchpad.net/cpe-foundation/commit/?id=4320902a