Issue 4069 - Drop SPDY in favour of HTTP/2

modules/nginx/templates/site.erb

 <% include_file = lambda do |url| %>
   <% content = Puppet::FileServing::Content.indirection.find(url) %>
   <% if content %>
     <%= content.content %>
   <% else %>
     <% raise StandardError, "Failed to resolve source URL #{url}" %>
   <% end %>
 <% end %>
 
 <% server_name = lambda do |domain, alt_names| %><%= domain %><% @alt_names.each do |name| %>, <%= name %><% end %><% end %>
@@ skipping 18 matching lines @@
     location /
     {
       rewrite (.*) https://$host$1 permanent;
     }
   }
   server
   {
     server_name <% server_name[domain, alt_names] %>;
 
     <% if is_default %>
-      listen 443 ssl spdy default_server;
-      listen [::]:443 ssl spdy default_server;
+      listen 443 ssl http2 default_server;
+      listen [::]:443 ssl http2 default_server;
     <% else %>
-      listen 443 ssl spdy;
-      listen [::]:443 ssl spdy;
+      listen 443 ssl http2;
+      listen [::]:443 ssl http2;
     <% end %>
 
     ssl_certificate <%= certificate %>;
     ssl_certificate_key <%= private_key %>;
 
     add_header Strict-Transport-Security max-age=31536000;
 <% else %>
   server
   {
     server_name <% server_name[domain, alt_names] %>;
@@ skipping 22 matching lines @@
 }
 
 <% if @content %>
   <%= content %>
 <% end %>
 
 <% if @source %>
   <% include_file[source] %>
 <% end %>
 }