BUG/MINOR: lua: Segfaults with wrong usage of types.

BUG/MINOR: lua: Segfaults with wrong usage of types.

Patrick reported that this simple configuration made haproxy segfaults:

    global
        lua-load /tmp/haproxy.lua

    frontend f1
        mode http
        bind :8000
        default_backend b1

        http-request lua.foo

    backend b1
        mode http
        server s1 127.0.0.1:8080

with this '/tmp/haproxy.lua' script:

    core.register_action("foo", { "http-req" }, function(txn)
        txn.sc:ipmask(txn.f:src(), 24, 112)
    end)

This is due to missing initialization of the array of arguments
passed to hlua_lua2arg_check() which makes it enter code with
corrupted arguments.

Thanks a lot to Patrick Hemmer for having reported this issue.

Must be backported to 1.8, 1.7 and 1.6.