BaseObject#getListValue cause the document metadata dirty flag to be set to true

A pre-condition is to have the document metadata dirty flag to be forced to false before that call.

The following trace lead to setting the flag to true while using getListValue obviously does not modify any metadata:

XWikiDocument.setMetaDataDirty(boolean) line: 2148	
DBStringListProperty(BaseProperty<R>).setValueDirty(boolean) line: 316	
ListProperty$NotifyList.setOwner(ListProperty) line: 316	
DBStringListProperty(ListProperty).getList() line: 187	
DBStringListProperty(ListProperty).getValue() line: 87	
BaseObject(BaseCollection<R>).getListValue(String) line: 494	

The problem seems to be that the ListProperty#NotifyList has its own dirty flag (which is totally useless as far as I can) and this flag is not resetted when the document flag is resetted, so it's stay to true.