[Winlogbeat] Skip add_host_metadata for forwarded event logs

[andrewkroh]

What does this PR do?

Update config examples to use the "forwarded" tag to skip adding host metadata.

Also disable host.name being added by libbeat. This field was overwritten by
the winlog.computer_name so it didn't serve any purpose to have libbeat set it.

Relates #13920

Why is it important?

Having host.* fields populated with data from the system on which the event occurred is important for interpreting and reacting to the data.

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.

Related issues

Relates #13920

Use cases

When reading from ForwardedEvents in a Windows Event Collector (WEC) setup you don't want the WEC machine using it's own host metadata in forwarded events. This solves that problem.

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request [Winlogbeat] Skip add_host_metadata for forwarded event logs #18153 updated]

• Start Time: 2020-05-04T14:19:37.033+0000

• Duration: 115 min 37 sec (6876582)

• Commit: 5ff2233

Test stats 🧪

Test	Results
Failed	0
Passed	7688
Skipped	1210
Total	8898

Steps errors

Expand to view the steps failures

• Name: Make -C generator/_templates/metricbeat test

  • Description: make -C generator/_templates/metricbeat test

  • Result: FAILURE

  • Duration: 1 min 57 sec<

  • Start Time: 2020-05-04T15:12:37.422+0000

• Name: Make -C generator/_templates/beat test

  • Description: make -C generator/_templates/beat test

  • Result: FAILURE

  • Duration: 1 min 18 sec<

  • Start Time: 2020-05-04T15:22:22.191+0000

• Name: Make -C generator/_templates/metricbeat test

  • Description: make -C generator/_templates/metricbeat test

  • Result: FAILURE

  • Duration: 1 min 18 sec<

  • Start Time: 2020-05-04T15:36:00.864+0000

• Name: Make -C generator/_templates/beat test

  • Description: make -C generator/_templates/beat test

  • Result: FAILURE

  • Duration: 2 min 38 sec<

  • Start Time: 2020-05-04T15:42:24.881+0000

[leehinman]

LGTM