In attachCursorToPipeline we catch StaleDbVersion and StaleShardVersionError exceptions, but in theory we should not, as 
sharding::router::CollectionRouter already handles this type of errors.

But if we remove them, we just fail with "Exceeded maximum number of 10 retries attempting .. sharding status of collection ... is not currently known and needs to be recovered"
 
This means that somewhere we don't handle config refresh correctly.