i made a symlink to fail2ban-client
ln -s /usr/bin/fail2ban-client /usr/bin/fail2ban
rebooted, ran the ispconfig update in the installer directory. ispconfig is still showing the message "fail2ban is not installed at this server."
output of which fail2ban is now
fail2ban is running, as far as i can tell.
service fail2ban status
Fail2ban (pid 4498) is running...
|- Number of jail: 0
`- Jail list: