[cisco_ftd] Add TLS system test

[taylor-swanson]

What does this PR do?

• Add system test for TLS using TCP input
• Fix issues flagged by check

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.

How to test this PR locally

cd packages/cisco_ftd && elastic-package test system

Related issues

• Relates Firewall Integration Input Consistency  #1878

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Build stats

• Start Time: 2022-05-12T07:54:49.163+0000

• Duration: 18 min 45 sec

Test stats 🧪

Test	Results
Failed	0
Passed	19
Skipped	0
Total	19

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (1/1)	💚
Files	100.0% (1/1)	💚 3.597
Classes	100.0% (1/1)	💚 3.597
Methods	100.0% (17/17)	💚 11.753
Lines	66.522% (1073/1613)	👎 -22.591
Conditionals	100.0% (0/0)	💚

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