fix(dccd): fix removals reporting

@jbdeboer / someone could you please review this, I'd like to merge it today.

The problem was that we keep a linked list of removed element but the the next and previous links were never resetted.

Then it could happen that we get a wrong value in `_reinsertAfter` (ie a value from a previous `_check`).

It used to work in checked mode where the links were resetted in `assert()`s