Otherwise we would see: "(Scope(Class[Tails::Reprepro::All])) Could
not look up qualified variable
'tails::reprepro::snapshots::params::architectures'; class
tails::reprepro::snapshots::params has not been evaluated"

Previously, tails::reprepro::all both declared
tails::reprepro::snapshots::* (that inherit from
tails::reprepro::snapshots::params), _and_ it used
tails::reprepro::snapshots::params's parameters to fetch default
values for its own parameters, so we were asking Puppet to solve
a chicken'n'egg situation.

refs: #6299