Fixed page duplication rendering bug

During CO-32063, we found a pdf rendering bug that introduces invisible text from the back page to the front page.

Investigation points to a iText bug while handling `position: absolute;` elements where content beyond page bound also gets rendered.

This PR applies the patch mentioned in https://code.google.com/p/flying-saucer/issues/detail?id=191

Also, why do you have an extra root layer check that doesn't exist in the patch/