Support fact stringyfication

FacterDB/rspec-puppet-facts have an option switch the symbolized
first-level keys in a factset to strings (all following/nested keys are
always strings). This PR makes this configuration opt-in so we can
switch over modules from symbols to strings in their spec files.

config_defaults.yml

@@ -112,6 +112,7 @@ spec/acceptance/nodesets/ec2/windows-2016-base-x64.yml:
   delete: true
 spec/spec_helper.rb:
   add_mocked_facts: true
+  facterdb_string_keys: false
   mock_with: false
 spec/spec_helper_acceptance.rb:
   unmanaged: true

moduleroot/spec/spec_helper.rb.erb

@@ -8,7 +8,7 @@
 ENV['COVERAGE'] ||= 'yes' if Dir.exist?(File.expand_path('../lib', __dir__))
 
 require 'voxpupuli/test/spec_helper'
-<%- if @configs['hiera_config'] || @configs['mock_with'] -%>
+<%- if @configs['hiera_config'] || @configs['mock_with'] || @configs['facterdb_string_keys'] -%>
 
 RSpec.configure do |c|
 <%- if @configs['hiera_config'] -%>
@@ -17,6 +17,7 @@ RSpec.configure do |c|
 <%- if @configs['mock_with'] -%>
   c.mock_with <%= @configs['mock_with'] %>
 <%- end -%>
+  c.facterdb_string_keys <%= @configs['facterdb_string_keys'] %>
 end
 <%- end -%>
 <%- if @configs['add_mocked_facts'] -%>