MBWI: several changes, debug output removed

This is a very "unsafe commit", since it adds new functionalities,
removes debug output and actualy makes the system crash if MBWI is
enabled. Anyway, this seems needed to better understand how to
proceed further.

This commit:

 - removes utterly cluttered debug output
 - add the notion of a per-server CPU (to keep track of where servers resides)
 - move set_proxy_execution a bit down, to reduce race conditions windows
 - disable throttling/replenishmet (to simplify things a bit)

Good luck! :/