Refactor Puppet class adblockplus::log::uplink

[matze]

... which has been introduced before #3638, but can undergo some major improvements as soon as class adblockplus::host has been merged:

• Use a fully qualified rsa_public_key instead of the legacy $ssh_public_key fragment
• Use the official $fqdn
• Remove unused parameters not examined, like $role and $groups
• Fetch default values from the Adblockplus::Host instance of the same $name

In addition, future use may focus on ensure_resource() calls on-demand, instead of relying on parameter $adblockplus::hosts and function create_resources().

[matze]

In the context of #3825 class adblockplus::log::uplink is removed, hence this ticket here is considered obsolete.