Revision 39074

  From S. Ryu:
  - Fix issue affecting the result of subsequent worker activation/deactivation requests when worker
    ordinal numbers were not in increasing order
  From me:
  - Add support for block requests for worker activation/deactivation (much more efficient, because
    FindUniqueSlaves is only called once); the list of workers to have their statis changed is comma-
    separated.
  - Make DeactivateWorker and ActivateWorker to return != 0 when something went wrong, with -2 indicating
    that at least one of the worker ordinal numbers in the list is invalid (e.g. '0.134' for a cluster
    with 20 workers only).