Phantom controller after a failed bootstrap

[Leon]

3.4.3-genericlinux-amd64.
I have the rook-ceph microk8s addon enabled, and hostpath-storage disabled.

A bootstrap fails,

```
k8s substrate "microk8s/localhost" added as cloud "microk8s-cluster" with storage provisioned
by the existing "ceph-rbd" storage class.
You can now bootstrap to this cloud by running 'juju bootstrap microk8s-cluster'.
Creating Juju controller "k8s" on microk8s-cluster/localhost
Bootstrap to Kubernetes cluster identified as microk8s/localhost
Creating k8s resources for controller "controller-k8s"
ERROR failed to bootstrap model: creating controller stack: creating statefulset for controller: timed out waiting for controller pod: pending: -
WARNING destroy k8s model timeout
ERROR error cleaning up: context deadline exceeded
ERROR No controllers registered.

Please either create a new controller using "juju bootstrap" or connect to
another controller that you have been given access to using "juju register".
```

And now the controller list is empty,

```
$ juju controllers
ERROR No controllers registered.

Please either create a new controller using "juju bootstrap" or connect to
another controller that you have been given access to using "juju register".

$ cat /home/ubuntu/.local/share/juju/controllers.yaml
controllers: {}
```

but the failed bootstrap left a phantom controller:

```
$ juju bootstrap microk8s-cluster k8s
ERROR a controller called "k8s" already exists on this k8s cluster.
Please bootstrap again and choose a different controller name.
```

The cloud init script to reproduce this:
https://github.com/canonical/cos-lite-bundle/pull/115