update nginx_version fact to check for kernel not equal windows

lib/facter/nginx_version.rb

@@ -1,6 +1,6 @@
 Facter.add(:nginx_version) do
   setcode do
-    if Facter::Util::Resolution.which('nginx')
+    if Facter.value('kernel') != 'windows' && Facter::Util::Resolution.which('nginx')
       nginx_version = Facter::Util::Resolution.exec('nginx -v 2>&1')
       %r{^nginx version: nginx\/([\w\.]+)}.match(nginx_version)[1]
     end