[BUGFIX] Set TYPO3_DLOG constant in testing framework

The constant is undefined currently and hence leads to useless calls
to the devLog facility.
Set this constant to false by default to avoid that.

Resolves: #79588
Releases: master
Change-Id: I22f9c3ddb564ccd86b763672120bd5991c97fb79
Reviewed-on: https://review.typo3.org/51504


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>