Set content-type to application/json
Summary:
Elasticsearch really wants a raw json body and it fails to accept
the request as of es version 5.3
Test Plan:
Tested with elasticsearch 5.2 and 5.3.
Before this change 5.2 worked but 5.3 failed with
HTTP/406 "Content-Type header [application/x-www-form-urlencoded] is not supported" [1]
After this change, both worked.
[1] https://phabricator.wikimedia.org/P5158
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D17580