Fix X509CertError definition in Haskell codebase

Thanks Dato for catching this.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

htools/Ganeti/Errors.hs

@@ -88,7 +88,8 @@ $(genException "GanetiException"
   , ("UnitParseError", [excErrMsg])
   , ("ParseError", [excErrMsg])
   , ("TypeEnforcementError", [excErrMsg])
-  , ("X509CertError", [excErrMsg])
+  , ("X509CertError", [ ("certFileName", [t| String |])
+                      , excErrMsg ])
   , ("TagError", [excErrMsg])
   , ("CommandError", [excErrMsg])
   , ("StorageError", [excErrMsg])