Use the firewall role and the selinux role from the postfix role

[nhosoi]

• Introduce postfix_manage_firewall to use the firewall role to manage the smtp services. Default to false - means the firewall role is not used.

• Introduce postfix_manage_selinux to use the selinux role to manage the ports in the smtp services. Assign smtp_port_t to the smtp service ports. Default to false - means the selinux role is not used.

• Add the test check task tasks/check_firewall_selinux.yml for verify the ports status.

• Add meta/collection-requirements.yml.

[nhosoi]

[citest]

[richm]

[citest]

[nhosoi]

@richm, all the CI tests passed. Is it ready to merge? If the answer is yes, may I squash the two commits into one?