Allow running none driver with force on 1 CPU

[afbjorklund]

For running on killercoda

Closes #15609

---

Here is how to try minikube on the new killercoda:

https://killercoda.com/examples/scenario/ubuntu-simple

sudo apt update
sudo apt install -y conntrack socat

curl -LO https://github.com/Mirantis/cri-dockerd/releases/download/v0.3.0/cri-dockerd_0.3.0.3-0.ubuntu-focal_amd64.deb
sudo dpkg -i cri-dockerd_0.3.0.3-0.ubuntu-focal_amd64.deb

curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube_latest_amd64.deb
sudo dpkg -i minikube_latest_amd64.deb

minikube start --driver=none

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[afbjorklund]

Workaround (before this patch):

minikube start --driver=none --force --extra-config=kubeadm.skip-phases=preflight