When a key is present in json object multiple times it doesn't raise a parse error and only last value is used. This should instead raise json_parse_exception.

Elasticsearch version: verified on 2.x, 5.0.0-alpha3

Steps to reproduce:

1. curl -X PUT localhost:9200/i -d '{"settings": {"number_of_replicas": 2}, "settings": {"number_of_shards": 1}}'
2. curl -X GET localhost:9200/i