More stuff for benchmark
Completely rewrote locking

* using a mutex for critical sections on linux is
  a bad idea - as they are far away from fair and
  linux ignores POSIX/pthread sched_* capability
  to set it to i.e. round robin
* old solution starved I/O threads, underutilizing
  nodes
* now we do not lock on a messenger level but on a
  work-item forwarding level and assert RR
  ourselves.