Revert "Reverse the sort order correctly when replacing default collections."

This reverts commit 5391a5d05c2534f4632e10f5a9cd10d3135a466c.

It causes Jenkins to fail with plone.app.blob in Plone 4.3 on Python
2.7.  This can't possibly have anything to do with this change, but
that has probably been said before, so let's make sure by reverting.