We don't have to update the RDN index up to the top when moving an entry

When we move an entry, we update all the ascendants up to the root, in order to update the number of descendants.

We can save us a few updates by stopping when we met the common ascendant, because it will have the same descendant number.

For instance, moving an entry from A/B/C/D/xxx to A/B/E/F/xxx will decrement the nbSubordinate counter for C and D, increment it for E and F, but for B, it will remain the same.

Doing so, in this very example, we would save 4 updates, dividing by 2 the number of updates.