[COOK-2743] tests run successfully now with Chef 11.4.0

```
BUNDLE_GEMFILE=test/support/Gemfile bundle exec rake test
/Users/mma/.rvm/rubies/ruby-1.9.3-p327/bin/ruby -I"lib:lib" -I"/Users/mma/.rvm/gems/ruby-1.9.3-p327/gems/rake-10.0.4/lib" "/Users/mma/.rvm/gems/ruby-1.9.3-p327/gems/rake-10.0.4/lib/rake/rake_test_loader.rb" "test/ntp/attributes_spec.rb"
Run options: --seed 37149

# Running tests:

.....................

Finished tests in 0.033757s, 622.0932 tests/s, 710.9637 assertions/s.

21 tests, 24 assertions, 0 failures, 0 errors, 0 skips
```