sftp: requireAdmin is true by default

for existing installs, it is off for backward compatibility

src/ldap.js

@@ -579,8 +579,7 @@ function loadSftpConfig(req, res, next) {
     addons.getServicesConfig('sftp', function (error, service, servicesConfig) {
         if (error) return next(new ldap.OperationsError(error.toString()));
 
-        const serviceConfig = servicesConfig['sftp'];
-        req.requireAdmin = serviceConfig && 'requireAdmin' in serviceConfig ? serviceConfig.requireAdmin : true;
+        req.requireAdmin = servicesConfig['sftp'].requireAdmin;
 
         next();
     });