Show an API failure message if the request failed.
Also take this opportunity to show a message in case
there are no notifications at all.
Bug: T136467
Change-Id: If5761ec3d3df10a8774561bed06a4ade54458c4b
Changing the way Echo's front-end architecture works to work with
model-view-controller methodology.
Change-Id: I97862402c41bc04dd41cd08d79f19ff677340249