Looks like I am indeed passing that option in the config.
[root@im ~]# ps aux | grep openfire
root 8101 0.0 0.0 5132 672 pts/0 S+ 10:53 0:00 grep openfire
daemon 30564 377 11.5 1296912 478564 ? Sl Apr27 3113:34 /opt/openfire/jre/bin/java -server -Djava.net.preferIPv4Stack=true -DopenfireHome=/opt/openfire -Dopenfire.lib.dir=/opt/openfire/lib -classpath /opt/openfire/lib/startup.jar -jar /opt/openfire/lib/startup.jar