Enhance distro support

[fnoop]

Add explicit Debian 9 (stretch) support, and add support for Ubilinux.

Ubilinux 4 (that supports all variants of the Up boards) is a derivative of Debian 9. However it reports dolcetto as the lsbdistcodename instead of stretch so the nginx repo fails. This PR adds support for a $nginx::repo_release parameter that allows the distro code name to be specified rather than blindly taking it from lsbdistcodename.

    class { 'nginx':
        manage_repo     => true,
        repo_release    => "stretch",
    }

See:
voxpupuli/puppet-nodejs#342

[wyardley]

I wonder if it would maybe be better to approach this just with another case in params (or with data in modules if #1155 gets merged?

[ekohl]

You can actually pass undef to puppetlabs-apt and let the module handle it meaning you don't need to pick: using $release will just work.

[fnoop]

Good point, changed in b85c060

[bastelfreak]

@fnoop can you add Ubilinux and Debian 9 to the metadata.json? Are you also interested in adding Ubilinux to facterdb? This is a gem with a list of mocked facts. This is heavily used for our unit testing (without that we can't test for Ubilinux).

[bastelfreak]

We should also add debian 9 to the acceptance test matrix if this is now working.

[bastelfreak]

@fnoop can you please rebase?

[wyardley]

Closing via #1200; thanks for the contribution.

[fnoop]

Apologies wasn't able to find time to rebase and finish this off, thanks for doing it :)