jormungandr: Error handling in stat_manger for RabbitMQ

When rabbitMQ is re-initialized and jormungandr is running,
jormungandr cannot push stat masage to rabbitMQ even if
the connection exists.

If it happens the connection will have to be re-initialized.
     logging.getLogger(__name__).exception('Server went away, will be reconnected..')

this way we have the message of the exception and the stacktrace