private void sendUnexpectedError() {
        sendError(new PacketError( PacketError.Condition.unexpected_request ));
    }
Send an error if a XEP-0198 stanza is received at an unexpected time.
e.g. before resource-binding has completed.
xmppserver/src/main/java/org/jivesoftware/openfire/streammanagement/StreamManager.java