This is done by moving
        self.replicator.populate()
after the switch to MasterOperationHandler, so that the latter is not delayed.

This change comes with some refactoring of the main loop,
to clean up app.checker and app.replicator properly (like app.tm).

Another option could have been to process notifications with the last handler,
instead of the first one. But if possible, cleaning up the whole code to not
delay handlers anymore looks the best option.