Alertmanager notifier: make it match the new notifier interface
Alertmanager notifier: make it match the new notifier interface

Signed-off-by: Thibault Chataigner <760b602e41777d70d0be9acf5dc7a32f8153d50b@criteo.com>

grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana,grafana/grafana