Inconsistent reading of txn vars from Lua script

[Joao Morais]

Hello again! Here are the snippets running with 2.4-dev18 - docker image 
haproxy:2.4-dev18-alpine:

$ cat h.cfg
global
  log stdout format raw local0
  lua-load /tmp/h/svc1.lua
  lua-load /tmp/h/svc2.lua
defaults
  timeout server 1m
  timeout client 1m
  timeout connect 5s
  log global
listen l
  mode http
  bind :8000
  option httplog
  http-request lua.auth
  http-request use-service lua.send-failure

$ cat svc1.lua
core.register_action("auth", { "http-req" }, function(txn)
        txn:set_var("txn.code", 401, true)
end, 0)

$ cat svc2.lua
core.register_service("send-failure", "http", function(applet)
    response = applet:get_var("txn.code")
    if response ~= nil then
        applet:set_status(response)
    else
        applet:set_status(403)
    end
    applet:add_header("Content-Length", 0)
    applet:add_header("Content-Type", "text/plain")
    applet:start_response()
end)

Now curl’ing the config above:

$ curl -i localhost:8000
HTTP/1.1 403 Forbidden
content-type: text/plain
content-length: 0

$ curl -i localhost:8000
HTTP/1.1 401 Unauthorized
content-type: text/plain
content-length: 0

The first run is always a 403 which means that the reading of the txn.code 
retuned nil, all the next attempts correctly returns 401. Maybe I’m missing 
some kind of initialization here? Otherwise I’m happy to provide this as a 
GitHub issue.

~jm