LPS-29604 Make ProgressTracker serializable (cluster aware)
LPS-29604 Refactor to use new API
LPS-29604 Refactor to use new API in Test
LPS-29604 Either make the var HttpSession httpSession, or use the default jsp implicit var names "request" and "session" for Http* and our standard naming convention for vars for Portlet*. Yeah, not consistent, but at least it's consistently inconsistent.