Replaces yaml.load() with yaml.safe_load()
Replaces yaml.load() with yaml.safe_load()

Yaml.load() return Python object may be dangerous if you receive a YAML
document from an untrusted source such as the Internet. The function
yaml.safe_load() limits this ability to simple Python objects like integers or
lists.

Reference:
https://security.openstack.org/guidelines/dg_avoid-dangerous-input-parsing-libraries.html

Change-Id: I1793ee3484f51dd663052e367d86f96f2f7598ea

stackforge/gertty,openstack/gertty