rhel8cis_firewall_interface should be variable

[aaosopra]

Feature Request or Enhancement:

• Feature [ Change rhel8cis_firewall_interface in ansible_vars_goss.yml.j2 to take variable]
• Enhancement [Not everyone uses enp0s3 or enp0s8 network interface]

Summary of Request
Want to be able to control which network interfaces goss tests for.
Only allowing enp0s3 or enp0s8 creates false negatives

Describe alternatives you've considered
Disable the whole test

Suggested Code

in ansible_vars_goss.yml.j2:

rhel8cis_firewall_interface: {{ rhel8cis_firewall_interfaces }}

in defaults/main.yml

rhel8cis_firewall_interfaces: {{ ansible_default_ipv4.interface }}