Use Vagrant's built-in support for Ansible provisioner. This eliminates the need
for a hosts file, and simplifies the ansible config file.
Renames config from .ansible.cfg to ansible.cfg since Ansible expects the file
to be called ansible.cfg and be adjacent to Vagrantfile when using the Vagrant
provisioner.
Update the README with an entry for the fsid and monitor keys. We
dediced to remove every key from the default variables.
Signed-off-by: Sébastien Han <sebastien.han@enovance.com>