Add rubocop-performance gem
This is needed to fix rubocop
warnings in CI eg:
$ BUNDLE_GEMFILE=../ci/Gemfile bundle exec rake --rakefile ../ci/Rakefile ${RAKE_TARGET}
cannot load such file -- rubocop-performance
[...]
RuboCop failed!
Running RuboCop...
Together with that we add a Puppetlabs module to make sure they don't blow up.