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: Iab51ca23786bb18911cdb4dd640ce2726f63ca30

stackforge/cloudkitty,openstack/cloudkitty,openstack/cloudkitty,stackforge/cloudkitty