[BUGFIX] EXT:form - fluid 2.2.0 compatibility

With the update of fluid to 2.2.0 (e0041459) the backend and frontend
break. This patch fixes these problems.

Change-Id: I74617650c5feff381421e15f50aa84aeaf2f6aad
Resolves: #79439
Releases: master
Reviewed-on: https://review.typo3.org/51410


Tested-by: Andreas Steiger <typo3@andreassteiger.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Daniel Lorenz <daniel.lorenz@extco.de>
Tested-by: Daniel Lorenz <daniel.lorenz@extco.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>