Add mention of --directory to useraddcern

docs/docs/account-mgmt.md

@@ -3,8 +3,8 @@
 <h2>How to configure LDAP to access user account information</h2>
 
 There are different ways to configure user accounts at CERN.
-If you only need to create a few AFS accounts, you should simply use
-the <tt>useraddcern</tt> command.
+If you only need to create a few local accounts, you should simply use
+the <tt>useraddcern</tt> command with the <tt>--directory</tt> argument.
 <p>
 If you need to give access to larger groups of accounts, that are centrally
 managed in FIM / Active Directory, read on...