Global dedup() in reducing by() of group() detaches elements for OLTP

When elements are detached they are not re-attached and thus prevent anything following `group()` from traversing them. For example:

g.V().both().
        group().by().by(out().dedup().fold()).
        unfold().
        select(Column.values).
        unfold().
        out()

When dedup() detaches the later attempt to traverse out() will produce no output as there are no edges on a detached object. I think we need to keep detachment in place for OLAP sake where I think this approach was envisioned.