let inspec set the default attribute for chef node attributes (#283)

Prevents #282 with InSpec >= 1.38.4

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>

README.md

@@ -541,7 +541,7 @@ node.override['audit']['chef_node_attribute_enabled'] = true
 ... and then use it in your profile:
 
 ```ruby
-chef_node = attribute('chef_node', description: 'Chef Node', default: {})
+chef_node = attribute('chef_node', description: 'Chef Node')
 
 control 'no-password-auth-in-prod' do
   title 'No Password Authentication in Production'