Allow role/pve-subscribe to fail on incompatible target without failing
the entire playbook run. This allows the playbook to easely setup the
environment against non-proxmox targets.
This commit introduces a new inventory host variable:
pve_enterprise=False
If set to True, apt sources and environment on the target is configured for
subscribed operation. If set to False annoying "subscribe me" popups are
disabled and apt sources are configured to the no-subscription
repositorys. The default value is False.
Proxmox's default state after installation is similar to
pve_enterprise=True.
This Role must be called before first apt call.
