Canal charm deletes files managed by kubernetes-node-base

[John Blesener]

If you remove the canal charm from a model, it deletes the file /opt/cni/bin/host-local (https://github.com/charmed-kubernetes/layer-canal/blob/main/reactive/flannel.py#L267). This binary is actually installed by kubernetes-node-base layer (https://github.com/charmed-kubernetes/layer-kubernetes-node-base/blob/main/reactive/kubernetes_node_base.py#L65). If you re-add canal to the model, the file won't get added back and the CNI will be unable to assign IP addresses to new pods.