PRs to note changes in nftables

Hello, everyone.

I made some minor changes to the dockerfiles and firewalling for the nftables kernel module in EL9 environments and raised it to PR.

First, I tested it and found that connections to unwanted ports are dropped and shown as filtered in nmap test.

Since the firewall may not be enabled in environments that use the ip_tables kernel module, I think it would be a good idea to change the firewall kernel module to nftables or check for that kernel module during the build process so that it can be built.

As this is a PR for comparison, it was not developed with merge in mind, so it is recommended to use it as a reference only.