[SECURITY] Avoid logging sensitive information during authentication

In order to avoid logging sensitive information during authentication
using the logging framework, according log level DEBUG is used.

Resolves: #88230
Releases: master, 9.5
Security-Commit: 625428b6364308f9f07f331bd176110d01e6c2f2
Security-Bulletin: TYPO3-CORE-SA-2019-010
Change-Id: I3e19afad6937515e0f6e1ab0a1c6d7004d182b79
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60703


Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>