Results with no points should exclude columns and points

[pauldix]

The list series query returns results like this:

[
  {"name":"metrics_Box001001_system_mem_used","columns":["time","sequence_number"],"points":[]},
  {"name":"metrics_Box001002_pf_labels_wan_bytes_in","columns":["time","sequence_number"],"points":[]}
]

Since points is an empty array it should be excluded. Also, because there are no points, there should be no columns, and so columns should be excluded.