updating rootdse when change on rename cames from DRS

[Matthieu Patou]

Hello metze,

can you have a look at this changeset 8bd5c1e794 in my pseudobacklink tree ?

I want to be sure I get your remarks good yesterday.
I'll try to clean my branch this week end and then ask for a review 
pretty soon but right now I'd like to see if the modification is the one 
I understood, at 2AM and more I'm not 100% sure that my brain was OK to 
understand it !

Matthieu.