Final control plane node can never be deleted

[liztio]

/kind bug

What steps did you take and what happened:

1. Create a kind management cluster
2. create a capa cluster using capd
3. delete the capd cluster (using the changes in [0.1] Delete machines kubernetes-sigs/cluster-api#1180 so the machines get deleted first)
4. Control plane node fails to delete with an error like failed with exit code one

What did you expect to happen:

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

The cluster will try to find another control-plane node to run kubectl on, but of course no such container exists. It will therefore try to execute a command on a container with the name of the empty string, which doesn't exist.

Environment:

• Cluster-api-provider-docker version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[chuckha]

/priority important-soon

[chuckha]

/assign
/lifecycle active