Handle existing containerd instances automatically on Github Actions

[jnsgruk]

In a recent commit, I made the move to remove Docker, Containerd, etc. from the Github Actions runner before running the tests. This is because with these packages present, the k8s snap fails to bootstrap since it detects the presence of the /run/containerd directory.

I looked at specifying a bootstrap config file per the K8s snap docs, but simply specifying a single option then interferes with the rest of the bootstrap configuration - perhaps there is a way to use the default configuration and only specify the containerd-base-dir that I missed?

In any case, one possible solution would be to detect when concierge is running on a Github Actions runner and simply disable the containerd service and delete the socket in /run as a non-destructive measure.

[jnsgruk]

The K8s team are looking into providing a command-line option that will dump the default bootstrap configuration.

Once this is in place, I think the right route to solve this problem is to:

• Dump the default bootstrap config
• Modify the containerd-base-dir
• Bootstrap with the newly modified file

This should result in fairly minimal code changes.