[BUGFIX] TS-Editor: Save button in single edit mode doesn't save

Due to a change from type = image to a button the saving of
content was blocked by internal checks. Make check behave the same
like saving content in the EditDocumentController.

Resolves: #68816
Releases: master
Change-Id: Ic67782ca346589f58c97958148735e8667f30da4
Reviewed-on: http://review.typo3.org/42362


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>