Support .rubocop.yml extensions and mocha mocking

Some extra items can now be added to the .sync.yml to customise templates.

code/.rubocop.yml:
  extra:
    Naming/VariableNumber
      Enabled: False

to extend code/.rubocop and in this case disable a check.

Also

code/spec/spec_helper.rb:
  mock_with: ':mocha'

to in this case enable use of the deprecated mocha for mocking.

So long as default mocking is left in tact we also now mock the systemd process so that the correct service provider is chosen within CI.

Tests with these changes:

• ai/it-puppet-module-bagplus!430
• it-puppet-module-ci_images!95 (closed)