Use commented object as context instead of comment within event trigger

- In order this to work with plone.contentrules use commented object as
  the main context within custom discussion events and add comment as the
  second parameter.

plone/app/discussion/comment.py

@@ -250,16 +250,20 @@ def notify_content_object_deleted(obj, event):
 def notify_comment_added(obj, event):
     """ Notify custom discussion events when a comment is added or replied
     """
+    conversation = aq_parent(obj)
+    context = aq_parent(conversation)
     if getattr(obj, 'in_reply_to', None):
-        return notify(ReplyAddedEvent(obj))
-    return notify(CommentAddedEvent(obj))
+        return notify(ReplyAddedEvent(context, obj))
+    return notify(CommentAddedEvent(context, obj))
 
 def notify_comment_removed(obj, event):
     """ Notify custom discussion events when a comment or reply is removed
     """
+    conversation = aq_parent(obj)
+    context = aq_parent(conversation)
     if getattr(obj, 'in_reply_to', None):
-        return notify(ReplyRemovedEvent(obj))
-    return notify(CommentRemovedEvent(obj))
+        return notify(ReplyRemovedEvent(context, obj))
+    return notify(CommentRemovedEvent(context, obj))
 
 def notify_content_object_moved(obj, event):
     """Update all comments of a content object that has been moved.