Busy loop that processes incoming WorkRequest messages via functions specified by add_command.
        Terminates if a command runs shutdown method

def process_messages_loop_internal(self):
        """
        Busy loop that processes incoming WorkRequest messages via functions specified by add_command.
        Terminates if a command runs shutdown method
        """
        logging.info("Starting work queue loop.")
        self.connection.receive_loop_with_callback(self.queue_name, self.process_message)