Support CentOS 8 Stream

[ekohl]

CentOS 8 Stream identifies itself without a minor version. This modifies the default to handle this. For completeness, the OS facts:

# facter os
{
  architecture => "x86_64",
  family => "RedHat",
  hardware => "x86_64",
  name => "CentOS",
  release => {
    full => "8",
    major => "8"
  },
  selinux => {
    enabled => false
  }
}

This is the first thing I found. I have not yet done a real test myself so for now this is a draft.

[ares]

Tested, this fixes the issue for me. 👍

[ekohl]

Closing because #1225 is a more complete solution.