Create swift operator keystone roles

Defining operator_roles in swift-proxy.conf requires
that these roles exist in keystone.

Because Keystone API access is not available on Swift
proxy hosts in most cases, operator_roles keystone
roles have been added to swift::keystone::auth class.

Added basic docs for swift::keystone::auth
Updated ensure_resource from latest PuppetLabs stdlib

Change-Id: I941c75e51898847ad346cdefbaa6ed7737dffc69
Related-Bug: #1251251
Merge "Create swift operator keystone roles"