kadmin: kadmind_dispatch do not write to 'out' on error

1b213c1082 ("kadmind: Add missing
error checks") altered the behavior of kadmin_dispatch() such that
it unconditionally called

  krb5_storage_to_data(rsp, out);

Previously kadmin_dispatch() only wrote to 'out' on success.
Doing so is important because 'rsp' might be NULL on error.

Change-Id: I2688a5c47db0f94d955971e785037c578d3f3fa4

kadmin/server.c

@@ -585,7 +585,8 @@ fail:
 	memset_s(password, len, 0, len);
 	free(password);
     }
-    krb5_storage_to_data(rsp, out);
+    if (ret == 0)
+	krb5_storage_to_data(rsp, out);
     krb5_storage_free(rsp);
     krb5_storage_free(sp);
     krb5_free_principal(contextp->context, princ);