TM: do not populate delivery service disabled locations

[rawlinp]

What does this PR (Pull Request) do?

The disabledLocations array is an unnecessary optimization for Traffic
Router, and it isn't always populated properly in certain cases, leading
to service outages. Therefore, never populate it, but keep the field
around for compatibility purposes.

• This PR fixes TM sometimes sets cachegroups to unavailable if all caches are ONLINE instead of REPORTED #6048

Which Traffic Control components are affected by this PR?

• Traffic Monitor

What is the best way to verify this PR?

Ensure the TM tests pass.
Shut down all caches in a cachegroup for a CDN, request GET /publish/CrStates from TM, ensure that the disabledLocations arrays are all empty -- i.e. [].

If this is a bug fix, what versions of Traffic Control are affected?

5.1.x, master

The following criteria are ALL met by this PR

• This PR includes tests OR I have explained why tests are unnecessary
• bug fix, no docs necessary
• This PR includes an update to CHANGELOG.md
• This PR includes any and all required license headers
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

[mattjackson220]

code looks good, TM tests pass, tested locally in CiaB and works as expected!