Is this a BUG REPORT or FEATURE REQUEST?:

/kind bug

What happened:
On a fresh Ubuntu 16.04.3 system booted from the official cloud image, kubeadm init fails because /var/lib/kubelet exists.

root@kubemaster:~# kubeadm init
[kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters.
[init] Using Kubernetes version: v1.8.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks
[preflight] Some fatal errors occurred:
        /var/lib/kubelet is not empty
[preflight] If you know what you are doing, you can skip pre-flight checks with `--skip-preflight-checks`

What you expected to happen:
kubeadm successfully initializes the cluster

How to reproduce it (as minimally and precisely as possible):

1. Boot a new VM from the latest Ubuntu Cloud image
2. apt-get install -y apt-transport-https docker.io
3. Follow the kubeadm installation instructions
4. kubeadm init

Anything else we need to know?:
Contents of /var/lib/kubelet:

/var/lib/kubelet
/var/lib/kubelet/pki
/var/lib/kubelet/pki/kubelet.crt
/var/lib/kubelet/pki/kubelet.key

Environment:

• Kubernetes version (use kubectl version):

  root@kubemaster:~# kubectl version
  Client Version: version.Info{Major:"1", Minor:"8", GitVersion:"v1.8.0", GitCommit:"6e937839ac04a38cac63e6a7a306c5d035fe7b0a", GitTreeState:"clean", BuildDate:"2017-09-28T22:57:57Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}
  The connection to the server localhost:8080 was refused - did you specify the right host or port?
  
  root@kubemaster:~# apt search kube
  Sorting... Done
  Full Text Search... Done
  kubeadm/kubernetes-xenial,now 1.8.0-01 amd64 [installed]
    Kubernetes Cluster Bootstrapping Tool
  
  kubectl/kubernetes-xenial,now 1.8.0-00 amd64 [installed,automatic]
    Kubernetes Command Line Tool
  
  kubelet/kubernetes-xenial,now 1.8.0-00 amd64 [installed,automatic]
    Kubernetes Node Agent
  
  kubernetes-cni/kubernetes-xenial,now 0.5.1-00 amd64 [installed,automatic]
    Kubernetes CNI
  

• Cloud provider or hardware configuration: Hyper-V generation 1 virtual machine
• OS (e.g. from /etc/os-release):

  NAME="Ubuntu"
  VERSION="16.04.3 LTS (Xenial Xerus)"
  ID=ubuntu
  ID_LIKE=debian
  PRETTY_NAME="Ubuntu 16.04.3 LTS"
  VERSION_ID="16.04"
  HOME_URL="http://www.ubuntu.com/"
  SUPPORT_URL="http://help.ubuntu.com/"
  BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
  VERSION_CODENAME=xenial
  UBUNTU_CODENAME=xenial
  

• Kernel (e.g. uname -a): Linux kubemaster 4.4.0-96-generic #119-Ubuntu SMP Tue Sep 12 14:59:54 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
• Install tools: none
• Others: none