Add RHEL7 SELinux support for new service_name_v6 param, subsequently fix puppet lint error

[wilson208]

This originally started as a fix for a puppet lint issue in CI, where the $seluser variable had been removed from the firewall::linux::redhat class as seluser property for the File["/etc/sysconfig/${service_name}"] resource is now set in a case statement.

When a separate PR was merged adding the 'service_name_v6' param, it still used the $seluser variable to set the seluser property of the File["/etc/sysconfig/${service_name_v6}"] resource.

When both these PR's were merged they then caused a puppet lint error in CI.

[ferventcoder]

I'd prefer to see the additional fields be added as a separate commit than the lint fixes.

[wilson208]

@ferventcoder I began with solving the lint issue. However I noticed the lint issue was because the $seluser variable had been removed and the result of solving the lint issue is this PR. I didn't add the additional service_name_v6 param, it was added in PR #641, and the variable $seluser was removed in PR #658. The PR for 641 was created in June and not merged until last week, which is why this was missed when david made his changes in #658 at the end of november.

[ferventcoder]

Now I better understand what is going on after looking closer.

[ferventcoder]

Minor nit* - would love to see the git commit message summary be around 50 chars with a message body. I looked over history for this repo and didn't find any long summaries.