I was able to get this working by changing the variable type to 'reference', and using the following code:
function onChange(control, oldValue, newValue, isLoading) {
//Type appropriate comment here, and begin script below
var newHire = g_form.getValue('new_hire_name');
var user = new GlideRecord('sys_user');
user.addQuery('sys_id', newHire);
user.query(setLocation);
function setLocation (user){
if ( user.next() ){
g_form.setValue('location_1', user.location);
g_form.setValue('location_2', user.location);
}
}
}
