vtc_haproxy: VTCP_listen_on 127.0.0.1 instead of localhost

    Always bind vtc_haproxy with 127.0.0.1 instead of binding on ::1 or
    127.0.0.1 depending on the environment.

    This is related to bug https://github.com/haproxy/haproxy/issues/937
    here the ipv6 and ipv4 are randomly mixed which can't work with socks4.