Dual Stack node-ip parameter is incorrect

[Jeremy Brisko]

When deploying dual stack Charmed Kubernetes the kubelet node-ip argument stays as either an IPv4 address, or an IPv6 address. This should be modified in dual stack to be (ipv4), (ipv6). The node needs to know about both addresses for pods using host networking. Otherwise they think they are running on a single stack network. As far as I can tell the function get_node_ip (https://github.com/charmed-kubernetes/layer-kubernetes-common/blob/ee2c0dc0bac647514c92148706d0887ba925c4cf/lib/charms/layer/kubernetes_common.py#L968) just needs to check for dual stack and apply both ingress addresses to the parameter.

[George Kraft (cynerva)]

Thanks for the report. We will need to be careful to make sure we don't break other code that calls get_node_ip. The only other reference I can find is in kubernetes-worker[1], which will need to be updated to properly account for multiple addresses.

[1]: https://github.com/charmed-kubernetes/charm-kubernetes-worker/blob/5f408eefde950022afca62ad077650659b81da63/reactive/kubernetes_worker.py#L597