fix to not cancel Trust Bundle watch when another upstream is available

[dhiaayachi]

Description

This fix the generated clusters for imported Peering upstreams in a specific scenario where there are multiple imported services on the same peer that have intentions to a single downstream service. In that specific scenario if one of the upstream services is removed from the list of services returned by the health endpoint while another is still available, this could result into the Trust Bundle watch being canceled.

The trust bundle watch is after used to create the relevant clusters associated with the healthy service in the down stream service and will result to those cluster not being generated (because we skip generation if the Trust Bundle is not available). In that case the following log is produced:

peer trust bundle not ready for discovery chain target:

The situation will resolve it self next time the Trust Bundle watch is initialized and triggered but in the mean time this could result in a loss of connectivity from the downstream service to the upstream imported service.

Testing & Reproduction steps

Links

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern