[BUGFIX] ImpExp: Do not show error message for recursive relations

Having recursive relations of records is a valid use case and must
not trigger an error message.

Releases: master, 7.6, 6.2
Resolves: #72709
Change-Id: I22a6216bca69fad33ab99387524965728757c057
Reviewed-on: https://review.typo3.org/45896


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>