Reloadable secure settings or restart master

[amih90]

I am trying to configure Google Cloud Storage for snapshot and restore by following
this tutorial.

After I add the credentials via elasticsearch-keystore, I should reload the secure settings by
POST _nodes/reload_secure_settings according to the API version 6.4.
https://www.elastic.co/guide/en/elasticsearch/reference/6.4/secure-settings.html#reloadable-secure-settings

but the request fail!
{ "error":"Incorrect HTTP method for uri [/_nodes/reload_secure_settings] and method [POST], allowed: [GET]", "status":405 }
when trying with GET I received
{"_nodes":{"total":0,"successful":0,"failed":0},"cluster_name":"myesdb","nodes":{}}
which I infer it didn't reloaded. In addition to the error i get when trying to create a snapshot
curl -X PUT "my_ip:9200/_snapshot/my_gcs_repository" -H 'Content-Type: application/json' -d' { "type": "gcs", "settings": { "bucket": "mybucket", "client": "my_cliend" } }

I've tried restart the service inside the pod but I couldn't manage it.
executing /elasticsearch/bin/elasticsearch fails because elasticsearch cannot restart by root.

1. when elasticsearch version will bump to 6.4?
2. how I can reload settings in keystore in the current version?
3. there is a way to restart elasticsearch service within the pod?

Thank you