[BUGFIX] Extension config: Write LocalConfiguration only if needed

The extension configuration is currently written by the
install tool silent updater each time the install tool
is entered, even if no configuration detail changed.
This is unfortunate on systems with read-only LocalConfiguration
since the install tool then throws an early fatal.
Prevent that write operation in case nothing changed.

Change-Id: I70d419690bcb633049ffcc9546e660d2f3b75a4c
Resolves: #83616
Releases: master
Reviewed-on: https://review.typo3.org/55413


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>