[SECURITY] prevent updating extension info by non-authorized users

Change-Id: I921c3ddcb4aee074a64dd78abcbc621d01fbba54
Reviewed-on: http://review.typo3.org/31764
Reviewed-by: Christian Zenker <typo3@xopn.de>
Tested-by: Christian Zenker <typo3@xopn.de>
Reviewed-by: Thomas Löffler <loeffler@spooner-web.de>
Tested-by: Thomas Löffler <loeffler@spooner-web.de>