ASN test fixes

[ericholguin]

Fixes #7033

Fixes issue mentioned above, and cleans up test code, increase test coverage by checking the ASN's fields.

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Which Traffic Control components are affected by this PR?

• Traffic Ops Tests

What is the best way to verify this PR?

Run TO integration tests

PR submission checklist

• [x] This PR has tests
• [ ] This PR has documentation
• [ ] This PR has a CHANGELOG.md entry
• [x] This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)