[BUGFIX] Fix 1-2-3(-4) wizard

Due to the localconf.php refactoring the 
install wizard is broken. This change fixes it.

Change-Id: I1e266a76c5cdbee140df47fd61a09a14c72be9b6
Releases: 6.0
Resolves: #39112
Reviewed-on: http://review.typo3.org/13028
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel