[BUGFIX] Set correct DB configuration in step installer

After the doctrine merge, the configuration for the database name changed.
Reflect this also in the database select step, when the user chooses
to select an empty existing database.

Releases: master
Resolves: #75961
Change-Id: Ie49bf42dd2142736c4d99fe8297b688e833e1a23
Reviewed-on: https://review.typo3.org/47949


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>