(packaging) Fully qualify variables supplied by the packaging repo in templates

Part of the variable scoping overhaul within the packaging repo was ensuring
the data about builds lives inside module Pkg::Config. In other projects, we
only use variables set by the packaging repo in templates, which means we can
pass the binding of the packaging repo Pkg::Config class into the template
engine and keep using "@" variables like we always have. But in puppetdb, we
mix data supplied by the packaging repo and data supplied by puppetdb itself in
the same template, which means we can't use just the Pkg::Config scope. Since
there are far more variables supplied by puppetdb in the templates than the
packaging repo, we opt to use the puppetdb scope and fully qualify access to
the variables supplied by the packaging repo, by referencing them as
Pkg::Config wherever we use them.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>