ctools_comment_render() should re-use comment_get_thread()

The database query in ctools_comment_render() is missing things like addTag('comment_filter') and addMetaData('node', $node) that is essential to allowing other modules to properly alter the query if necessary. I see no reason why it can't just re-use the function comment_get_thread() to return the list of comment IDs to render. If this was intentional to duplicate the code, I don't really see any compelling reasons why it can't be re-used.