The backwards compatibility test was failing intermittently due to two
related timing issues in the test setup.
The issue was that Dave's `wait_graph_sync dave 3` was hanging
for up to 60 minutes. Dave's initial gossip sync with Charlie could
complete before Charlie had forwarded the alice-bob channel
announcement, leaving Dave stuck at 2 channels until lnd's historical
syncer fired at its default interval of 1 hour. After this 1-hour idle,
some routing state had become stale, causing the subsequent payment from
alice to dave to fail with FAILURE_REASON_NO_ROUTE.
This issues is now addressed by setting `--historicalsyncinterval=10s` on
all nodes. This causes nodes to periodically re-sync the full gossip
state from their peers every 10 seconds instead of every hour. Dave
therefore picks up any missed channel announcements and routing policies
within seconds, and alice's routing graph stays up-to-date throughout
the test.
Additionally, lnd debug logs from all containers are now collected
before teardown on failure and uploaded as a CI artifact, making future
failures easier to diagnose.
ziggie