One-stop resource on how to effectively disable SSLv3 in major web browsers as well as in web, mail and other servers that may still be using it.
Edit the bind line in your /etc/haproxy.conf configuration file, and append no-sslv3.
For example:
bind :443 ssl crt <crt> ciphers <ciphers> no-sslv3
For more information see the HAProxy documentation.