Display a message when Onionoo is unavailable

Ticket #18080 (moved) prevents Globe from reading Onionoo resources. When this situation occurs Globe gets stuck with the loader image overlay. Instead Globe should detect Onionoo unavailability and display an message.

added component::metrics/relay search owner::irl priority::medium resolution::fixed severity::normal status::closed type::defect labels

We're shutting down Globe soon, but Atlas is likely affected by the same issue. Moving to the Atlas component.

Trac:
Component: Metrics/Globe to Metrics/Atlas
Owner: isis to phw
Reviewer: N/A to N/A

Trac:
Username: RaBe
Status: new to assigned
Owner: phw to RaBe

Atlas already was showing a "backend down" error message for search results, but there was a minor bug so the "Top 10" page got stuck with the loading icon if Onionoo was not reachable. Here's the fix:

https://github.com/RaphaelBergmann/atlas/commit/f0660990707ae9832456dd52d0bcf26c32eaed22

Trac:
Username: RaBe
Owner: RaBe to irl

Trac:
Username: RaBe
Status: assigned to needs_review

Merged. Thanks. (:

Trac:
Status: needs_review to closed
Resolution: N/A to fixed

closed