[BUGFIX] Property of alternative model implementation not found

The PersistentObjectConverter is mapping submitted data to a
given target domain model. If a class gets overloaded with
config.tx_extbase.objects, this information is not forwarded
to the ReflectionService. That's why properties in alternative
implementations cannot be determined.

Resolves: #49803
Releases: master, 6.2, 6.1
Change-Id: Ia4ec3a6c6f5bc6c07717a4956ab12e3e779c3c5a
Reviewed-on: http://review.typo3.org/33327
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>