Fix PyYAML load warning in k8s.io test.
Fix PyYAML load warning in k8s.io test.

For security purposes, PyYAML 5.1 has deprecated the use yaml.load()
without specifying a Loader. For more information on this deprecation,
see the PyYAML docs here:
https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation

kubernetes/k8s.io,thockin/k8s.io,thockin/k8s.io,kubernetes/k8s.io,thockin/k8s.io,kubernetes/k8s.io,kubernetes/k8s.io,thockin/k8s.io