Modernized

Hetzner has made some updates that allow us to update this role:

• ftype=1 is default now for Ubuntu, so I dropped support for mocking those options.
• Python 3.7 is shipped by default in recovery images, and Ansible supports it, so I switch to using it by default.
• The image search path was absurdly going up & down. Fixed.
• Use reboot plugin from Ansible. Requires 2.7.