[BUGFIX] Race condition in Unit / FunctionalTestBootstrap

Executing tests in parallel sometimes leads to race conditions
preparing the environment. This rare case is now just suppressed
and shut off.

Resolves: #66720
Releases: master
Change-Id: I63de8c8cf8460772d0896f1957701f053ca82590
Reviewed-on: http://review.typo3.org/39171


Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>