This revert commit bddc1802,
to fix the following storage crash:

  Traceback (most recent call last):
    ...
    File "neo/lib/handler.py", line 72, in dispatch
      method(conn, *args, **kw)
    File "neo/storage/handlers/master.py", line 44, in notifyPartitionChanges
      app.pt.update(ptid, cell_list, app.nm)
    File "neo/lib/pt.py", line 231, in update
      assert node is not None, 'No node found for uuid ' + uuid_str(uuid)
  AssertionError: No node found for uuid S3

Partitition table updates must also be processed with InitializationHandler
when nodes remain in PENDING state because they're not added to the cluster.