Foreign key err handling regex was not catching tables with _'s

[mhoppa]

What does this PR (Pull Request) do?

• This PR fixes To: INternal server error when server capability associated with Server/ds is deleted #4033

Which Traffic Control components are affected by this PR?

• Traffic Ops

What is the best way to verify this PR?

Create a server capability assign it to a server or ds and then attempt to delete it. It should now return a 400 instead of a 500.

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

master

The following criteria are ALL met by this PR

• This PR includes tests
• I have explained why documentation is unnecessary
• This PR includes an update to CHANGELOG.md OR such an update is not necessary
• This PR includes any and all required license headers
• This PR ensures that database migration sequence is correct OR this PR does not include a database migration
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Additional Information

[asf-ci]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/trafficcontrol-PR/4668/

[ocket8888]

All tests pass, manual test confirmed it works.