TP: do not mark DSR (ds request) complete if ds update fails due to validation error

[mitchell852]

• This PR fixes TP: error message doesn't display properly when fulfilling an invalid DSR immediately #5188

If DSRs are enabled in traffic_portal_properties.json and your user has the override role, when you make a change to an existing DS, you must create a DSR first and you have the following options:

If you have the override role, you will see the Fulfill Request Immediately option which will do 2 things:

1. it creates a DSR (for historical purposes) and sets it to "complete"
2. it updates the DS

However, if #2 fails API validation, the DSR should not be marked as "complete" but should rather be left in the "submitted" state so it can be modified per the error message.

Which Traffic Control components are affected by this PR?

• Traffic Portal

What is the best way to verify this PR?

• enable dsRequests in traffic_portal_properties.json, set overrideRole=admin, login as an admin user.
• make a change to an existing DS that you know will fail backend validation (see TP: error message doesn't display properly when fulfilling an invalid DSR immediately #5188 for example), fulfill DSR immediately. ensure error message is displayed in TP and a DSR is created but NOT marked as complete.

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

• master (5940129)
• 4.1.0
• 5.0.0 (RC1)

The following criteria are ALL met by this PR

• This PR includes tests OR I have explained why tests are unnecessary
• This PR includes documentation OR 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)

[rawlinp]

Tested, it works as the description says