test(inpsec): test apt-cacher client config

kitchen.yml

         base:
           '*':
             - apt-cacher.ng.server
+            - apt-cacher.ng.client
       pillars:
         top.sls:
           base:

test/integration/default/controls/config_spec.rb

     # Custom config
     its('content') { should include "Port: 9999" }
   end
+
+  describe file('/etc/apt/apt.conf.d/80proxy') do
+    # Default config
+    its('content') { should include 'Acquire::http::Proxy "http://localhost:9999";' }
+    its('content') { should include 'Acquire::https::Proxy "DIRECT";' }
+  end
 end