TO Integration test improvements

[ericholguin]

Adds the following improvements as suggested by the team:

• Make all caps http verbs constant for consistency instead of the strings they currently are
• Make sure all testCase fields start on their own newline for readability
• Remove the extra call to time.Now
• Add Require assertions (FatalNow) wherever necessary
• Add helper function call to the utils check functions

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Which Traffic Control components are affected by this PR?

• Traffic Ops Testing

What is the best way to verify this PR?

Run TO Integration tests

PR submission checklist

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