Submit device command executions.

        Returns: a list of concurrent.futures for scheduled executions.

def submit_commands(self, devices, execution):
        """Submit device command executions.

        Returns: a list of concurrent.futures for scheduled executions.
        """
        fs = []
        for device in devices:
            if device[key_id_] != self.device_id:
                logging.warning('Ignoring command for unknown device: %s'
                                % device[key_id_])
                continue
            if not execution:
                logging.warning('Ignoring noop execution')
                continue
            for command in execution:
                f = self.executor.submit(
                    self.dispatch_command, **command
                )
                fs.append(f)
        return fs