code: public double calculateNormalization(final List<ServerHolder> serverHolders)
    {
      double cost = 0;
      for (ServerHolder server : serverHolders) {
        for (DataSegment segment : server.getServer().getLazyAllSegments()) {
          cost += computeJointSegmentsCost(segment, segment);
        }
      }
      return cost;
    }
docs: Calculates the cost normalization.  This is such that the normalized cost is lower bounded
  by 1 (e.g. when each segment gets its own historical node).
  
  @param serverHolders A list of ServerHolders for a particular tier.
  
  @return The normalization value (the sum of the diagonal entries in the
  pairwise cost matrix).  This is the cost of a cluster if each
  segment were to get its own historical node.