Updates all the example provisioner scripts to use the new functions
exposed by the VMBuilder class as an illustration of how best to use
them.
Also adds a wrapper fail() handler to ensure the cleanup of the script,
as well as the global cleanup, are run on an exception.
1. Ensure that system_template and script are not nullable in the DB.
2. Ensure that the CLI and API enforce the above and clean up CLI
arguments for profile add.
3. Ensure that, before uploading OVAs, a 'default_ova' provisioning
script is present.
4. Use the 'default_ova' script for new OVA uploads.
5. Ensure that OVA details are properly added to the vm_data dict in the
provisioner vmbuilder.
Joshua Boniface