[BUGFIX] SYS_LASTCHANGED is only updated if page is viewed in live or no

workspace

The SYS_LASTCHANGED field was updated whenever which workspace was loaded,
leading to SYS_LASTCHANGED being updated while no content was 
published yet.
This patch changes this behavior by updating SYS_LASTCHANGED only if
page is viewed from the live workspace or no workspace at all.

Resolves: #42158
Releases: master
Change-Id: I09aca547a7b22ba1699f521ea7609053991fed4c
Reviewed-on: http://review.typo3.org/40259


Reviewed-by: Jan Helke <typo3@helke.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Frederic Gaus <frederic.gaus@flagbit.de>
Tested-by: Frederic Gaus <frederic.gaus@flagbit.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>