Override less Ansible settings (#224)

* Do not escalate privileges by default

* Do not disable host key checking by default

* Do not mute deprecation warnings by default

* Provide ansible.cfg only as an example

The new example file does ONLY contain options that are related to this
playbook.

* Remove explicit inventory path from scripts

The inventory file is specified in ansible.cfg, see README.md.

reboot.sh

@@ -1,3 +1,3 @@
 #!/bin/bash
 
-ansible-playbook reboot.yml -i inventory/my-cluster/hosts.ini
+ansible-playbook reboot.yml