Update vyos_ssh.py

[ovikosta]

Raise ValueError without call config_mode

[ktbyers]

Probably should exit_config_mode() also (if we are going to enter config mode).

Also you need output += on the second output capture (or it will overwrite the first output).

[ovikosta]

No problem and also add exit_config_mode() in function def commit()?

        output = self.config_mode()
        output += self._send_command_str(
            command_string,
            strip_prompt=False,
            strip_command=False,
            read_timeout=read_timeout,
        )