containerd charm configure to support for unsecure private registry (http)

[Zhanglei Mao]

The private registry shared by http ( not https) can not be used or correctly configure via
juju config custom_registries configure option

To reproduce it as:
juju config custom_registries a http private registry
and create a pod with it, it would still try to download with https and failed.

[Tim Van Steenburgh (tvansteenburgh)]

Unfortunately this behavior is caused by a bug in containerd, see https://github.com/containerd/cri/issues/1433.

[Joe Guo (guoqiao)]

Hi Tim,

As I can see containerd bug #1443 is now fixed.
However, I think there is also a bug in charm template[1]:

```
    [plugins.cri.registry]
      [plugins.cri.registry.mirrors]
        [plugins.cri.registry.mirrors."docker.io"]
          endpoint = ["https://registry-1.docker.io"]
    {% if custom_registries %}
      [plugins.cri.registry.auths]
      {% for registry in custom_registries %}
        {% if registry.username and registry.password %}
        [plugins.cri.registry.auths."{{ registry.url }}"]
          username = "{{ registry.username }}"
          password = "{{ registry.password }}"
        {% endif %}
      {% endfor %}
      [plugins.cri.registry.configs]
      {% for registry in custom_registries %}
        {% if registry.ca or registry.cert or registry.key or registry.insecure_skip_verify %}
        [plugins.cri.registry.configs."{{ registry.url }}".tls]
          ca_file = "{{ registry.ca if registry.ca else '' }}"
          cert_file = "{{ registry.cert if registry.cert else '' }}"
          key_file = "{{ registry.key if registry.key else '' }}"
          insecure_skip_verify = {{ "true" if registry.insecure_skip_verify else "false" }}
        {% endif %}
      {% endfor %}
    {%
```

According to doc[2], we expect config like this for new registry:

    [plugins.cri.registry]
      [plugins.cri.registry.mirrors]
        ...
        [plugins.cri.registry.mirrors."34.235.169.214:5000"]
          endpoint = ["http://34.235.169.214:5000"]
        ...

However, that is not rendered by template at all.

[0]: https://jaas.ai/u/containers/containerd#charm-config-custom_registries
[1]: https://github.com/charmed-kubernetes/charm-containerd/blob/a35726e8f908ba8fef5fc9000c0e5ee850ac9ae0/templates/config.toml#L63
[2]: https://github.com/containerd/cri/blob/master/docs/registry.md#configure-registry-endpoint

[Adam Dyess (addyess)]

This should be resolved as of
https://github.com/charmed-kubernetes/charm-containerd/pull/43