These are notes from the whiteboard in the Big Room concerning
metrics configuration:

1 The metrics exemplar starts out *empty*.

2 After command-line arguments are parsed, if the exemplar contains
  no Hop Count metric, add a Hop Count metric to the exemplar at
  its *end*.

3 Do not pack a Hop Count metric into a Hello/LSU if that Hop Count
  metric is at the end of the metrics vector.