cli_utils: Use yaml.safe_load instead of yaml.load
yaml.load is unsafe (can call arbitrary Python code) and throws a DeprecationWarning these days
Test Plan
tox
Migrated from D1398 (view on Phabricator)
Staging instance, all changes can be removed at any time
yaml.load is unsafe (can call arbitrary Python code) and throws a DeprecationWarning these days
tox
Migrated from D1398 (view on Phabricator)