Lookup cache: bubble up error results without modifying

[patrickmann]

Resolves #19159

Description

Lookup cache needs to distinguish between empty results and error results. The latter should not be altered, in particular the TTL.

How Has This Been Tested?

Unit test

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Refactoring (non-breaking change)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.