Add `validate` option to lineinfile module to edit the sshd config file in chapter 10

[geerlingguy]

To prevent users from blowing up their SSH server configuration and locking them out from their servers, we can add a validate to the lineinfile example modifying the sshd_config file in Chapter 10. For example, we created the following task in the May 20 Ansible 101 livestream (see #269):

    - name: Make sure SSH is more secure.
      lineinfile:
        dest: /etc/ssh/sshd_config
        regexp: "{{ item.regexp }}"
        line: "{{ item.line }}"
        state: present
        validate: 'sshd -t -f %s'
      with_items:
        - regexp: "^PasswordAuthentication"
          line: "PasswordAuthentication no"
        - regexp: "^PermitRootLogin"
          line: "PermitRootLogin no"
        - regexp: "^Port"
          line: "Port 2849"
      notify: restart ssh

[FinalDes]

Need to check sshd service is started first before run the command, ortherwise will have error,
my molecule test fail because sshd service is not started

- name: start sshd service
  become: true
  systemd:
    name: sshd
    state: started

[FinalDes]

planning to add https://github.com/jtesta/ssh-audit the check ssh is secure or not.
PasswordAuthentication no require additional checks. Need to check public key is install first, otherwise cannot access to ssh server

[geerlingguy]

Fixed in the book's manuscript. Will be in the next book version.