test(config): fix for Amazon Linux 2 & Oracle Linux 7/8

test/integration/default/controls/config.rb

 server_available = '/etc/nginx/sites-available'
 server_enabled	 = '/etc/nginx/sites-enabled'
 
-# Override by OS
-case os[:name]
-when 'redhat', 'centos', 'fedora'
+# Override by platform family
+case platform[:family]
+when 'redhat','fedora'
   server_available = '/etc/nginx/conf.d'
   server_enabled   = '/etc/nginx/conf.d'
-when 'opensuse'
+when 'suse'
   server_available = '/etc/nginx/vhosts.d'
   server_enabled   = '/etc/nginx/vhosts.d'
 end

test/integration/default/controls/service.rb

   title 'should be running and enabled'
 
   describe service('nginx') do
+    it { should be_installed }
     it { should be_enabled }
     it { should be_running }
   end