Disable upgrading of single-word addresses in Safari
Here, you are actually searching for a word in your default search engine and go to the first hit. You can either type http:// before your host name or if you have control over that host name, try to change it to example.local or similar which contains a dot (.). 

Also, after the first use if http://example to visit that page (putting http:// manually), next time you will be able to use the hostname without the hassle to put `http' first. Till you remove it from history.