[BUGFIX] Workspace page previews collide with generated preview links

Workspace page previews collide with that configuration that might have
been set by using a preview link containing a ADMCMD_prev command. The
keyword "IGNORE" is introduced to actually ignore these configurations
when viewing a page from the workspace module.

Resolves: #72225
Releases: master, 7.6, 6.2
Change-Id: I6a73e860a76308028f0a3b1bcd182e41082adcd6
Reviewed-on: https://review.typo3.org/45253


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>