Don't fail when there is no .kube dir

[schnatterer]

Following #1, I tried this on a plain ubuntu (I used multipass) and it actually failed when there was no kubeconfig:
./scripts/init-cluster.sh: line 97: /home/ubuntu/.kube/config2: No such file or directory

multipass launch --name gitops 20.04
multipass shell gitops
sudo apt update && sudo apt install -y docker.io
sudo usermod -aG docker ubuntu
exit
multipass shell gitops
git clone https://github.com/cloudogu/k8s-gitops-playground
cd k8s-gitops-playground

git switch feature/init-without-kubectl

yes | scripts/init-cluster.sh

This should fix it.
It also checks our only prerequisite left: docker binary present and fails otherwise.