Install conntrack to pass CI/CD with K8s 1.18

[nolar]

What do these changes do?

Fix the CI/CD tests with Kubernetes 1.18, which now requires conntrack.

Description

Since Kubernetes 1.18 release (since 25.03.2020), the CI/CD tests are broken:

error execution phase preflight: [preflight] Some fatal errors occurred:
	[ERROR FileExisting-conntrack]: conntrack not found in system path

This PR fixes it.

Issues/PRs

Issues: fixes #334

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• Mostly CI/CD automation, contribution experience

Checklist

• The code addresses only the mentioned problem, and this problem only
• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt

[zincr]

🤖 zincr found 0 problems , 0 warnings

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✅ Approvals
✅ Specification
✅ Dependency Licensing

[zincr]

🤖 zincr found 1 problem , 0 warnings

❌ Approvals
✅ Large Commits
✅ Specification
✅ Dependency Licensing

Details on how to resolve are provided below

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Approvals

All proposed changes must be reviewed by project maintainers before they can be merged

Not enough people have approved this pull request - please ensure that 1 additional user, who have not contributed to this pull request approve the changes.

• ✅ Approved by PR author @nolar
• ❌ 1 additional approval needed