[BUGFIX] Install tool: Trigger ext scan on ext open

In the extension scanner, if opening a single extension view
for the first time, the scanner is correctly triggered again.

Change-Id: I72d18a17d735d67109135205684f25c75dc77711
Resolves: #82140
Related: #76084
Releases: master
Reviewed-on: https://review.typo3.org/53744


Tested-by: TYPO3com <no-reply@typo3.com>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>