This does NOT require restart of SSH

cat << 'EOL'>~/.ssh/config
Host *
    StrictHostKeyChecking no
    UserKnownHostsFile /dev/null
    LogLevel=quiet
EOL
chmod 400 ~/.ssh/config

https://askubuntu.com/questions/87449/how-to-disable-strict-host-key-checking-in-ssh/385187#385187

http://www.shiftedbytes.com/2013/12/how-to-hide-warning-permanently-added.html