When updating bugs do not print email address if using --print-fas-names
    
    For public display we do not want to share our user's email address more
    than that. So we have an --print-fas-names action mapping back the email
    to an username.
    This commit makes the logic that updates open bugs when the default
    assignee changes honor this flag.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>