[BUGFIX] Check for LocalConfiguration to identify a firstInstall scenario

Introduced by #68261
After the logout from the install tool backend module
the FIRST_INSTALL page was shown instead of the
install tool locked page.

Fixes: #68343
Releases: master
Change-Id: I0df80a72509695e37bc5a9ccf6a2c443126ddd28
Reviewed-on: http://review.typo3.org/41680


Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>