Upgrade from 2.1.1 to 2.2.0: field _id is defined twice elasticsearch

Elastic Stack Elasticsearch
2

I'm seeing this as well

This bulk indexing request now fails in 2.2.0

{"index":{"_index":"test_5zogjdzthm_v2","_type":"test","_id":"obj_5"}}
{"id":"obj_5","created_at":"2016-02-11T11:32:43.184Z","updated_at":"2016-02-11T11:32:43.184Z","_type":"test"}

The fix is obvious: don't repeat the _type in the object.