sameer.ganu,
CA/Rally did not build nor do we support this Integration. If I had to guess, I assume it was built using one of the Web Services API versions prior to Portfolio Items being introduced or they don't handle the PortfolioItem/Feature Structure in their connector. I don't have any experience with it and there really isn't much information I can find about it. I do see at least one unanswered question on their forums asking this same question.
You may have more success posting your question on the Tableau Forums/Communities. Maybe someone who develops the Integration monitors those and can assist or, hopefully, there is someone else on this Community that has had experience with it.
Michael