[Cisco_ftd] adding missing ECS fields

[P1llus]

What does this PR do?

Adds missing ECS fields server and client

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.
• If I'm introducing a new feature, I have modified the Kibana version constraint in my package's manifest.yml file to point to the latest Elastic stack release (e.g. ^7.13.0).

[elasticmachine]

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• Start Time: 2021-09-15T10:23:00.278+0000

• Duration: 14 min 9 sec

• Commit: 2e5d24c

Test stats 🧪

Test	Results
Failed	0
Passed	17
Skipped	0
Total	17

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