Set sniff schema when elasticsearch `enableSniff` config is true

[abbat]

What changed?

By default elasticsearch client use http schema when sniff nodes (see DefaultScheme in olivere/elastic/client.go). This change set sniff schema to first host schema in config.

Why?

If elasticsearch cluster nodes works with httpS, sniffing works incorrect because add http (not httpS) discovered nodes.

How did you test it?

Run elasticsearch cluster with httpS nodes and set enableHealthcheck config to true. Before this change you will see "http://<node>:9200 is dead" messages (due http schema).

Potential risks

Seems no risks still enableSniff is false by default and not used in config_template.yaml.

Documentation

No, enableSniff is not documented yet.

Is hotfix candidate?

No.

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This PR was marked as stale. Please update or close it.