[BUGFIX] Add button to lock install tool

This patch adds a button to lock the install tool again, also without login.

Resolves: #56640
Releases: master, 7.6
Change-Id: I6a4368376082288955eb20197ab437e893c93ffc
Reviewed-on: https://review.typo3.org/47555


Reviewed-by: Kay Strobach <typo3@kay-strobach.de>
Tested-by: Kay Strobach <typo3@kay-strobach.de>
Reviewed-by: Michael Oehlhof <typo3@oehlhof.de>
Tested-by: Michael Oehlhof <typo3@oehlhof.de>
Reviewed-by: Benjamin Kott <info@bk2k.info>
Tested-by: Benjamin Kott <info@bk2k.info>