fix for double challenge factor

[kabakakao]

These changes had to be made, if you need the stepup-factor. Without these changes the challenge "correctAnswer" isn't shown the second time

Description

Instead of setting the function _print_correct_answer to None this change checks if the answer is the same as in the first attempt.

Motivation and Context

In our organization we are using the "correctAnswer" Factor. And the stepup-auth is needed. So the factor came up twice. Without these changes it isn't shown the second time

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] 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.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[kabakakao]

@epierce any chance to get it merged? It is a really annoying issue for us. Please let me know, if I have to change anything.

[kabakakao]

This is Not needed anymore due to Code changes