Add a script to create OpenStack setup

The script does the following:

     - Checks if the host has enough free memory of at-least 10G
     - Creates 2 virtual machines
     - Imports the virtual machines into libvirt
     - Checks if nested virtualization is enabled or not
     - Enables host-passthrough on Compute node
     - Takes a libvirt QCOW2 internal snapshot of Controller and Compute
       nodes
     - Starts the virtual machines
Add some notes for create-ostack-nodes script