Updated ansible uri module HEADERS_ field

This fixes a deprecation warning that gets displayed when running
the kibana/post_config 'Get kibana default indexes' task.

HEADERS_ has been deprecated since ansible 2.1 and will be
removed in 2.9.

https://docs.ansible.com/ansible/latest/modules/uri_module.html

TrivialFix

Change-Id: I177113c606119505c6cb69c66a326f7cbdaf2196

ansible/roles/kibana/tasks/post_config.yml

@@ -42,7 +42,8 @@
 
 - name: Get kibana default indexes
   uri:
-    HEADER_Content-Type: application/json
+    headers:
+      Content-Type: application/json
     url: "{{ internal_protocol }}://{{ kolla_internal_vip_address }}:{{ elasticsearch_port }}/.kibana"
     method: GET
   register: kibana_default_indexes