Now which *host* is hosting a specific container is not defined in the
playbook yaml file but centrally in the invetory under the
`ansible_lxc_host` variable.

The `lxc_guest` role is runned directly against the guest, even if it
doesn't exist yet, and lxc tasks are delegated to the lxc-running
physical host.

In this way it should be easier to scale-up and configure multiple
istance of a service on different containers without changing the
playbook.

Look at `/ldap.yaml` for a commented example.

`lxc-ssh.py` removed.

All Playbbooks now user `ssh_lxc` connection.

`ansible_ssh_lxc_name` variable used to specify container name.

Tested and worked correctly with `python==3.8.2` and `ansible==2.9.6` on the
controller and `python==2.7` on the target.