Atomic host bootstrap

Atomic host testing has been done with the network plugin flannel. Change the inventory var kube_network_plugin: flannel.

Note: Flannel is the only plugin that has currently been tested with atomic

Vagrant

For bootstrapping with Vagrant, use box centos/atomic-host or fedora/atomic-host
Update VagrantFile variable local_release_dir to /var/vagrant/temp.
Update vm_memory = 2048 and vm_cpus = 2
Networking on vagrant hosts has to be brought up manually once they are booted.
```
vagrant ssh
sudo /sbin/ifup enp0s8
```
For users of vagrant-libvirt download centos/atomic-host qcow2 format from https://wiki.centos.org/SpecialInterestGroup/Atomic/Download/
For users of vagrant-libvirt download fedora/atomic-host qcow2 format from https://dl.fedoraproject.org/pub/alt/atomic/stable/

Then you can proceed to cluster deployment