Delete the security groups for each role in the cluster, and the group for
    the cluster.

def _delete_security_groups(self):
    """
    Delete the security groups for each role in the cluster, and the group for
    the cluster.
    """
    group_names = self._get_all_group_names_for_cluster()
    for group in group_names:
      self.ec2.delete_security_group(group)