In R81 sshd_config is replaced after each reboot. You need to do the following to make your changes permanent and survive reboot
Steps:
vi /etc/ssh/templates/sshd_config.templ (Make your changes)
/bin/sshd_template_xlate < /config/active
service sshd reload
Example:
sed -i 's/PasswordAuthentication no/PasswordAuthentication yes/' /etc/ssh/templates/sshd_config.templ
sed -i 's/PermitRootLogin forced-commands-only/PermitRootLogin yes/' /etc/ssh/templates/sshd_config.templ
/bin/sshd_template_xlate < /config/active
service sshd reload
