Adds nova snapshot to the compute node

Snapshot 'nova-compute_installed' will contain the following
packages

    1. nova-compute-qemu
    2. python-guestfs
    3. libguestfs-tools

Installs and configures nova compute services.

This snapshot can be used to obtain stable running version of
controller node and can be used to revert back to this point in case
the students break the cluster.

Change-Id: Ide59062b30fdd9bd8c44f1b9c3e606ef1433f720
Merge "Adds nova snapshot to the compute node"