Set zimbraAuthLdapExternalDn during user creation

zmldapsync/zmldapsync.pl

@@ -368,6 +368,7 @@ DOMAIN: foreach my $domain ( keys $conf->{domains} ) {
         $attrs .= ' ' . $conf->{domains}->{$domain}->{users}->{attr_map}->{$attr} . " " .
                   zim_attr_value( $ext_users->{$user}->{$attr} );
       }
+      $attrs .= " zimbraAuthLdapExternalDn " . zim_attr_value( $ext_users->{$user}->{dn} );
       # The password won't be used because Zimbra is set to use external LDAP/AD auth
       # But better to set it to a random value
       my $pass = $uuid->create_str;