processPeerings replaced the path map every run but kept the count of
paths dropped while the map was full, so every later "Processed AS
peerings" line reported all drops since start next to that run's own
figures. The count is now set to 0 where the map is replaced, under the
same lock. A test fills the map, has one path dropped, runs the
processing and finds the count back at 0.
Model: opus-5-5
sneak