global: update generation number also in clients without registry

Not all clients have an existing registry, and the registry generation
number will not be updated for them.  However, we would like to check
for stale globals also elsewhere, eg.  metadata, and it must work also
in this case.

To avoid failing to update client registry generation, on global
addition which the client would see if it had a registry, send done
message for the new global id instead.

src/modules/module-protocol-native/protocol-footer.h

@@ -44,7 +44,6 @@ struct footer_core_global_state {
 };
 
 struct footer_client_global_state {
-	uint64_t last_sent_generation;
 };
 
 struct footer_demarshal {