Enable Ability to Configure SELinux for Oracle Linux

[jswongF5]

Proposed changes

We installed Oracle Linux on our VMWare Cluster. We noticed the SELinux configuration is like any other rhel OS so would like to enable ability to configure this by setting the nginx_selinux variable in this role.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• [ ] I have read the CONTRIBUTING document
• [ ] I have added Molecule tests that prove my fix is effective or that my feature works
• [ ] I have checked that any relevant Molecule tests pass after adding my changes
• [ ] I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md)