[TASK] Use a 401 header if login is not successful

If login is not correct, a 401 should be used instead of a 200.

Change-Id: Ia2fa139e89fe19df77bb0530b4fbce502506f524
Resolves: #51803
Releases: 6.2,6.1,6.0,4.5
Reviewed-on: https://review.typo3.org/23801
Reviewed-by: Markus Klein
Tested-by: Markus Klein