Update to use new Custom Resources format

[jsmartt]

Scenario/Intent

Make this cookbook support Chef 13+

Environment Details

• iLO Cookbook Version: 1.4.0
• iLO Appliance Type: All
• iLO Firmware Version: All
• chef-client Version: 13 or 14
• platform: All

Steps to Reproduce

1. Update the Gemfile from gem 'chef', '~> 12.5' to just gem 'chef'
2. Remove your Gemfile.lock if you have one
3. Run bundle install
4. Run rake unit

Expected Result

Test to pass

Actual Result

Lots of undefined local variable or method errors get raised. Apparently the ::property method in newer versions of chef don't make those properties available as methods with the same name.

See https://docs.chef.io/custom_resources_notes.html and https://docs.chef.io/custom_resources.html