You want to add these lines to /etc/ssh/sshd_config instead of /etc/ssh/ssh_config since you want to control the activity of the sshd daemon. Be sure to stop/restart the sshd daemon...
It sounds like the password for root has been wiped out. You should reboot your HP-UX server into single-user mode. Once you are at the prompt, you can then set the password for root using the...