Put passenger_app_env back in to passenger configuration (#5683)

closes #5682

roles/passenger/templates/passenger.j2

@@ -2,6 +2,7 @@ server {
   listen {{ passenger_listen_port }} default_server;
   server_name {{ passenger_server_name }};
   passenger_enabled {{ passenger_enabled }};
+  passenger_app_env {{ passenger_app_env }};
   passenger_set_header X-Forwarded-For $remote_addr;
   passenger_set_header    X-Real-IP        $remote_addr;
   root {{ passenger_app_root }};