cisco_ios: add missing event.original mapping

[efd6]

What does this PR do?

This adds the missing event.original mapping that should exist for when preserve_original_event is true.

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

• Check still valid for 8.1.
• Query why this absence was not identified by tests.

How to test this PR locally

elastic-package test

Related issues

• Closes [cisco_ios] Missing mapping for event.original #2634

Screenshots

N/A

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Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

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Build stats

• Reason: null

• Start Time: 2022-02-03T00:03:02.585+0000

• Duration: 19 min 24 sec

• Commit: fb9fa53

Test stats 🧪

Test	Results
Failed	0
Passed	9
Skipped	0
Total	9

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