title: Fragment not being removed from back stack
body: <p>I've noticed a strange behaviour when not adding a framgent transaction to the back stack. I have 4 fragments: A, B, C and D. The transaction for the C fragment isn't added to the back stack. First I add A, then B, then C. Then I press BACK. A is displayed,  which is normal. Then I add D and I press BACK. The result is that the fragment C is displayed. Is there something I am missing, because I would expect C to be out of the back stack and to see fragment A.</p>