Setting of auto properties depends on specific Jackrabbit behviour

The post servlet ignores a ConstraintViolationException when trying to set an auto property (SlingPropertyValueHandler#setProperty method. This has been introduced by SLING-1619

According to SLING-2763 this is specific Jackrabbit behaviour and might fail with other implementations (e.g. Oak) as the check might not occur when setting the property but when saving.

Looking at the comments of SLING-1619, I'm not sure if adding this check for the ConstraintViolationException was the right thing to do anyway.