[TASK] Avoid incomplete test setup in MFA tests

The MFA tests have an indirect dependency to FE/BE
state of request. This is dealt with in other tests
already, but a few are missing. Add proper setup.

Resolves: #104771
Releases: main
Change-Id: I9561cd810c90423692d941c40a3e5a9351889396
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85823


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>