Updating kubernetes-dashboard image in a Azure acs-k8s cluster is not getting reflected
It will be getting updated but then reverted by the k8s addon manager. If you ssh into a master the templates for the addon services live in etc/kubernetes/addons.
To upgrade the image you can edit /etc/kubernetes/addons/kubernetes-dashboard-deployment.yaml and change image inside the Deployment spec.
Your change should be picked up in a few seconds.