fix(centos): fix tests

test/integration/default/controls/gems_spec.rb

@@ -9,7 +9,7 @@ control 'Wanted/Required gems' do
     minitest
   ]
   case platform[:name]
-  when 'amazon'
+  when 'centos', 'amazon'
     wanted.delete('minitest')
   end
 

test/salt/pillar/redhat.sls

@@ -28,7 +28,11 @@ packages:
   gems:
     wanted:
       - progressbar
-      - minitest
+      # minitest requires Ruby version ~> 2.2.
+      # ruby 2.0.0p648 (2015-12-16) [x86_64-linux]
+      # https://stackoverflow.com/a/50931910
+      # $ sudo amazon-linux-extras install ruby2.6
+      # - minitest
     unwanted:
       - diff-lcs
       - kitchen-vagrant