Charmed Kubernetes should support series upgrade

[Cory Johns]

All charms used in Charmed Kubernetes should support series upgrade.

* kubernetes-master will need to ensure that HA fail-over works as expected during the upgrade and set an appropriate status during the upgrade.

* kubernetes-worker will need to drain the node, stop the services, and set an appropriate status during the upgrade.

* kubeapi-load-balancer is currently a SPoF and will need to be made HA to support series upgrade.

* easyrsa just needs to set an appropriate status (originally reported at https://bugs.launchpad.net/charm-easyrsa/+bug/1850121).

* etcd will need to stop the service and set an appropriate status during the upgrade (originally reported at https://bugs.launchpad.net/charm-etcd/+bug/1850124).

* The runtime and CNI subordinates don't really need to do anything since the node is drained by k8s-worker.

[Cory Johns (johnsca)]

While it would be ideal to have the subordinates stop their services during the upgrade, the pre-series-upgrade hook seems to fire on subordinates before the principal. Because of this, stopping the services would interfere with the worker's ability to drain the pods. During testing, leaving them running didn't have any obvious impact on the cluster's function.

[Cory Johns (johnsca)]

Added the rest of the charms because even for the CNI, container runtime, and integrator charms, we need to at least set an appropriate status. For AWS-IAM, I'm not certain yet if it will work to stop the service before that master is brought down, but if it does, we should do so. keepalived similarly needs some additional research, but I think we will probably want to bring it down prior to the kubeapi-load-balancer.

[Cory Johns (johnsca)]

Charm PRs:

https://github.com/charmed-kubernetes/charm-aws-iam/pull/3
https://github.com/juju-solutions/charm-aws-integrator/pull/39
https://github.com/juju-solutions/charm-azure-integrator/pull/23
https://github.com/charmed-kubernetes/layer-calico/pull/53
https://github.com/charmed-kubernetes/layer-canal/pull/50
https://github.com/charmed-kubernetes/charm-containerd/pull/35
https://github.com/CanonicalLtd/docker-registry-charm/pull/43
https://github.com/charmed-kubernetes/charm-docker/pull/14
https://github.com/charmed-kubernetes/layer-easyrsa/pull/25
https://github.com/charmed-kubernetes/layer-etcd/pull/170
https://github.com/charmed-kubernetes/charm-flannel/pull/60
https://github.com/juju-solutions/charm-gcp-integrator/pull/6
https://github.com/charmed-kubernetes/charm-kata/pull/5
https://github.com/juju-solutions/charm-keepalived/pull/9
https://github.com/charmed-kubernetes/charm-kubeapi-load-balancer/pull/5
https://github.com/charmed-kubernetes/charm-kubernetes-master/pull/87
https://github.com/charmed-kubernetes/charm-kubernetes-worker/pull/56
https://github.com/juju-solutions/charm-openstack-integrator/pull/31
https://github.com/charmed-kubernetes/layer-tigera-secure-ee/pull/26
https://github.com/juju-solutions/charm-vsphere-integrator/pull/4

[Cory Johns (johnsca)]

https://github.com/charmed-kubernetes/kubernetes-docs/pull/402

[Cory Johns (johnsca)]

https://github.com/charmed-kubernetes/jenkins/pull/589

[George Kraft (cynerva)]

No cherry-pick needed for keepalived 1.20+ck1 release.