[TASK] Add CLI option to set DB socket for functional tests

An additional option "typo3DatabaseSocket" can be set
to configure a custom DB socket when running functional tests
from the commandline interface.

Resolves: #61465
Releases: 6.3, 6.2
Change-Id: If34526264bdc8b91c7c45785dde06a10fb606526
Reviewed-on: http://review.typo3.org/32672
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>