Deb repository doesn't contain bionic

[emmetog]

Describe the bug
When running this role on Ubuntu 18.04.5 LTS (bionic) the installation fails:

TASK [ossec-agent : Debian/Ubuntu | Installing repository] **********************************************
fatal: [<<redacted>>]: FAILED! => {"changed": false, "msg": "apt cache update failed"}

Trying to add the repository manually gives "Access Denied". From a quick look it seems like this is because this repo doesn't support bionic.

The dj-wasabi/ansible-ossec-server role uses https://updates.atomicorp.com/channels/atomic/{{ ansible_distribution | lower }} {{ ansible_distribution_release }} while this role uses http://ossec.wazuh.com/repos/apt/{{ ansible_distribution | lower }} {{ ansible_distribution_release }}.

I suggest using atomicorp.com instead as it seems to work fine for bionic, or even better: make this repository url and key configurable.

Installation method/version
Installed the role using an ansible galaxy requirements file as follows:

- src: dj-wasabi.ossec-agent
  name: "ossec-agent"
  version: master

Actual commit used is 6c29671c64909b9e0feb0e202cd8a00258a81187 (latest master at the time)

Ansible Version

ansible 2.9.6
  config file = /home/emmet/code/<<redacted>>/ansible.cfg
  configured module search path = ['/home/emmet/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.8.2 (default, Jul 16 2020, 14:00:26) [GCC 9.3.0]

Targetted hosts
Concerns the following OS(es):

• Ubuntu 18.04.5 LTS (bionic)

Expected behavior
The install to be successful.

Additional context
If any more info is needed just ask.