Confine NGINX version fact to exclude Cisco Nexus

Cisco Nexus Switches may run older version of NGINX
internally in which the command 'nginx -v' disables
the nxapi socket (deletes sock file) on second or
later runs.  Tested on CIsco NXOS 9k. Refactor ruby
fact moving kernel/OS to confine block as well.

lib/facter/nginx_version.rb

@@ -1,6 +1,9 @@
 Facter.add(:nginx_version) do
+  confine do
+    Facter.value(:kernel) != 'windows' && Facter.value(:operatingsystem) != 'nexus'
+  end
   setcode do
-    if Facter.value('kernel') != 'windows' && (Facter::Util::Resolution.which('nginx') || Facter::Util::Resolution.which('openresty'))
+    if Facter::Util::Resolution.which('nginx') || Facter::Util::Resolution.which('openresty')
       nginx_version_command = Facter::Util::Resolution.which('nginx') ? 'nginx -v 2>&1' : 'openresty -v 2>&1'
       nginx_version = Facter::Util::Resolution.exec(nginx_version_command)
       %r{nginx version: (nginx|openresty)\/([\w\.]+)}.match(nginx_version)[2]