Cherry-pick #19168 to 7.x: Fix unused libbeat.config.module metrics

[andrewkroh]

Cherry-pick of PR #19168 to 7.x branch. Original message:

What does this PR do?

These metrics existed in the code but were unused and hence always 0.

"libbeat":{"config":{"module":{"running":0,"starts":0,"stops":0}

I updated the module reload code to increment and set the metrics when changes are applied.

Why is it important?

If the metrics are exposed by /stats then they should work, otherwise they are misleading.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Logs

I tested the metrics using Auditbeat module reloading:

  "libbeat": {
    "config": {
      "module": {
        "running": 1,
        "starts": 2,
        "stops": 1
      },
      "reloads": 2,
      "scans": 75
    },

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #19294 opened]

• Start Time: 2020-06-18T19:47:53.336+0000

• Duration: 79 min 35 sec

Test stats 🧪

Test	Results
Failed	0
Passed	9432
Skipped	1581
Total	11013