[Prometheus] Disable leader election; Remove default value for bearer token

[tetianakravchenko]

Signed-off-by: Tetiana Kravchenko tetiana.kravchenko@elastic.co

What does this PR do?

For cases when prometheus is running not on kubernetes, prometheus integration does not work:

• defined default value for bearer_token cause those errors:

{"log.level":"error","@timestamp":"2022-08-18T09:02:02.484Z","log.origin":{"file.name":"process/stdlogger.go","file.line":54},"message":"metricbeat_monitoring stderr: \"panic: close of closed channel\\n\\ngoroutine 2015 [running]:\\ngithub.com/elastic/beats/v7/metricbeat/beater.(*Metricbeat).Stop(0xc0009d44d0)\\n\\t/go/src/github.com/elastic/beats/metricbeat/beater/metricbeat.go:276 +0x28\\ngithub.com/elastic/beats/v7/libbeat/cmd/instance.(*Beat).launch.func5()\\n\\t/go/src/github.com/elastic/beats/libbeat/cmd/instance/beat.go:461 +0x68\\nsync.(*Once).doSlow(\"","agent.console.name":"metricbeat_monitoring","agent.console.type":"stderr","ecs.version":"1.6.0"}
{"log.level":"error","@timestamp":"2022-08-18T09:02:02.484Z","log.origin":{"file.name":"process/stdlogger.go","file.line":54},"message":"metricbeat_monitoring stderr: \"0xc0010807d0, 0xc001201c00)\\n\\t/usr/local/go/src/sync/once.go:68 +0x138\\nsync.(*Once).Do(0xc0010807d0, 0xc001201c00)\\n\\t/usr/local/go/src/sync/once.go:59 +0x45\\ngithub.com/elastic/elastic-agent-libs/service.HandleSignals.func1()\\n\\t/go/pkg/mod/github.com/elastic/elastic-agent-libs@v0.2.5/service/service.go:60 +0x20c\\ncreated by github.com/elastic/elastic-agent-libs/service.HandleSignals\\n\\t/go/pkg/mod/github.com/elastic/elastic-agent-libs@v0.2.5/service/service.go:49 +0x25c\\n\"","agent.console.name":"metricbeat_monitoring","agent.console.type":"stderr","ecs.version":"1.6.0"}

• enabled leader election works only on kubernetes

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes [Prometheus integration] leader election enabled for non k8s environment causing metricbeat crash  #3905

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• Start Time: 2022-08-23T11:21:27.095+0000

• Duration: 14 min 40 sec

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[gizas]

Adding the comment if can be out from advanced setttings.

As for k8s+prometheus the value needs to change to true and users will have to search to find it

[tetianakravchenko]

@gizas I've changed it and moved leader election from advanced settings