Restructure iteration over the counters we compare.
Restructure iteration over the counters we compare.

- Fix issue in read_config() that may return empty items in the counter
  list.
- Add iterable, get_all(data, key) to get the value of a key regardless
  of depth in the dictionary.
- Add better error handling around missing values in the comparison
  area.

arista-eosext/rphm