[BUGFIX] Only throw tooDirty if uid part of cleanProperties

AbstractEntity tooDirty Error should be thrown only if uid field is
actually part of the cleanProperties Array

Change-Id: I6b093b7363d4b7c1fdc0f823f7c1ef66bb07b532
Resolves: #8066
Releases: 6.1, 6.0
Reviewed-on: https://review.typo3.org/2655
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring