global_state: Make section optional

This section would be sent:

a- for all new machine types
b- for old machine types if section state is different form {running,paused}
   that were the only giving us troubles.

So, in new qemus: it is alwasy there.  In old qemus: they are only
there if it an error has happened, basically stoping on target.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

hw/ppc/spapr.c

@@ -1853,6 +1853,7 @@ static const TypeInfo spapr_machine_info = {
 static void spapr_compat_2_3(Object *obj)
 {
     savevm_skip_section_footers();
+    global_state_set_optional();
 }
 
 static void spapr_compat_2_2(Object *obj)