code: void initReplicaHome( H2ONode h2o, Key key ) {
      assert key.home();
      assert _key == null; // This is THE initializing key write for serialized Values
      assert h2o != H2O.SELF;     // Do not track self as a replica
      _key = key;
      // Set the replica bit for the one node we know about, and leave the
      // rest clear.
      _replicas.add(h2o._unique_idx);
      _rwlock.set(0);             // No GETs are in-flight at this time.
      //System.out.println(key+", init "+_rwlock.get());
    }
docs: Initialize the _replicas field for a PUT.  On the Home node (for remote
  PUTs), it is initialized to the one replica we know about, and not
  read-locked.  Used on a new Value about to be PUT on the Home node.