crdt: fixed consistency bug
crdt: fixed consistency bug

Found by attempted correctness proof and not by testing as it requires
unordered links or message loss with at least four concurrent requests
in a specific interleaving.

scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris