Queues roster feeds whose topology the cache lacks, and starts the walk
when none is running. Nothing is queued while the global sweep is the
one bringing topology in (it covers every feed), nor for a feed already
loaded, loading or queued.
Parameters
feedIDs: number[]
Candidate feed IDs (a sync's arrivals, or the roster).
Queues roster feeds whose topology the cache lacks, and starts the walk when none is running. Nothing is queued while the global sweep is the one bringing topology in (it covers every feed), nor for a feed already loaded, loading or queued.