Make CI work under Ubuntu 20

[phansch]

Fixes #125

[phansch]

https://github.com/FGtatsuro/ansible-vagrant fails to install because it attempts to install a python-pip package which doesn't exist in Ubuntu 20.04

[phansch]

Disabled the ansible-vagrant installation for now.

Next up: shutter is not available in the ubuntu 20.04 repos anymore.

[phansch]

Getting a weird failure with cron:

TASK [Backup cron] *************************************************************

fatal: [localhost]: FAILED! => {"changed": false, "msg": "Failed to find required executable crontab in paths: /code/.venv/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"}

But crontab should be installed with 43f7d83?

[phansch]

Next error: fatal: [localhost]: FAILED! => {"changed": false, "msg": "crontab: user 'phansch' unknown\n"}}