(IAC-1228) Allow File.read to passthrough for JSON spec tests

In the context of Puppet 7 there are two subsequent calls to
File.read from the catalog generated from the tests of `loadjson_spec.rb`
and `load_module_metadata_spec.rb`

Prior to this commit, these calls were causing exceptions from
RSpec as the mock expectations for File.read were being thrown off.

This did not manifest on Puppet 5 or 6.

After this commit, any calls to File.read that do not conform to
the expected arguments we want to mock a response for, are passed
through to File.read.

Author: Ciaran McCrisken

spec/functions/load_module_metadata_spec.rb

@@ -7,6 +7,8 @@
 
   describe 'when calling with valid arguments' do
     before :each do
+      # In Puppet 7, there are two prior calls to File.read prior to the responses we want to mock
+      allow(File).to receive(:read).with(anything, anything).and_call_original
       allow(File).to receive(:read).with(%r{\/(stdlib|test)\/metadata.json}, :encoding => 'utf-8').and_return('{"name": "puppetlabs-stdlib"}')
       allow(File).to receive(:read).with(%r{\/(stdlib|test)\/metadata.json}).and_return('{"name": "puppetlabs-stdlib"}')
       # Additional modules used by litmus which are identified while running these dues to being in fixtures

spec/functions/loadjson_spec.rb

@@ -6,6 +6,8 @@
 
   describe 'when calling with valid arguments' do
     before :each do
+      # In Puppet 7, there are two prior calls to File.read prior to the responses we want to mock
+      allow(File).to receive(:read).with(anything, anything).and_call_original
       allow(File).to receive(:read).with(%r{\/(stdlib|test)\/metadata.json}, :encoding => 'utf-8').and_return('{"name": "puppetlabs-stdlib"}')
       allow(File).to receive(:read).with(%r{\/(stdlib|test)\/metadata.json}).and_return('{"name": "puppetlabs-stdlib"}')
       # Additional modules used by litmus which are identified while running these dues to being in fixtures