clarify policy on the original name

tsa/doc/naming-scheme.mdwn

@@ -87,8 +87,7 @@ designate network, gateway and broadcast addresses, but also in
 [[howto/ganeti]], where networks are managed automatically for virtual
 machines.
 
-The first network was named `gnt-fsn`, for `Ganeti in the Falkenstein
-datacenter`. Future networks should be named `FUN-LOCNN-ID` (example
+Future networks should be named `FUN-LOCNN-ID` (example
 `gnt-fsn13-02`) where:
 
  * `FUN` is the function (e.g. `gnt` for [[howto/ganeti]])
@@ -96,3 +95,7 @@ datacenter`. Future networks should be named `FUN-LOCNN-ID` (example
  * `ID` is a two-character number, padded with zero, starting from
    one, to distinguish multiple instances at the same
    function/location pair
+
+The first network was named `gnt-fsn`, for `Ganeti in the Falkenstein
+datacenter`. That naming convention is considered a legacy exception
+and should not be reused. It might be changed in the future.