Don't reply to notification message

The notification listener doesn't have anything to send to the notifier
and the notifier doesn't attend to receive something.

So this patch remove the message reply when the listener is a
notification
listener.

Partial implements blueprint notification-subscriber-server

Change-Id: Ic989947ba3b6894cde788422842fca19159ea261
Make the dispatcher responsible of the message ack

This patch make the dispatcher responsible of the message
acknowledgement.

This is the preliminar step to be able to requeue message.

Partial implements blueprint notification-subscriber-server

Change-Id: If74b47d5e23976d407deb27df7395b1982963c75