Fix upsert _id field handling.
Fix upsert _id field handling.

Oddly, this wasn't happening locally, but is erroring on the CI. Maybe a
difference between MongoDB 2 vs 3 as a server.

NREL/api-umbrella,NREL/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,apinf/api-umbrella,NREL/api-umbrella,apinf/api-umbrella,NREL/api-umbrella