Author: Frédéric Lécaille <flecaille@haproxy.com>
    Date:   Mon Jul 15 15:20:07 2019 +0200

    Open and close a TCP socket to simulate an unreachable server.

    This is done for each haproxy instance. The socket address (resp. port)
    may be referenced by ${<name>_closed_addr} (resp. ${<name>_closed_port})
    variable where <name> is the haproxy instance name.