Add support for post-deployment provisioning.

 * This change adds provisioning for:

   - demo usage - adds demo tenant, cirros image, and configures
     quantum networking
   - tempest configuration - checks out the tempest tree and
     configures tempest.conf to work with resources provisioned
     for demo usage
   - ovs external bridge configuration - ensures that the ovs external
     bridge is correctly configured to support VM connectivity via
     floating ips

 * Only a single-host deployment is supported at present, due to:

   - the openstack puppet modules presuming local access to the
     different services' configuration files (e.g. /etc/nova/nova.conf)
   - the ovs bridge configuration only being valid for a single-host
     deployment.

Change-Id: I485baedfe63ba90d221b6e376eb5d5aeb14e0d93