Use SafeYAML.load to avoid YAML monkeypatch in safe_yaml.

[fnichol]

This will leave YAML loading in Test Kitchen as implementation detail
and avoid polluting other Ruby objects.

[damm]

Just keep in mind eventually we will get past the limits of sanity and need to creating more ground.

People seem to be giving YAML a bad rap over these exploits. The truth is that all of these exploits exist in any scheme that allows you to create arbitrary objects in a target system. This is why nobody uses Marshal to send objects around. Think of YAML as a human readable Marshal.

YAML f7u12