RequestQueue locks might get lost in specific scenarios

[janbuchar]

Error scenario

1. fetch and lock 25 requests in RequestQueue, lock time is 60s
2. each takes 10s, which is within the request handler timeout
3. after a couple of requests, the "locally dequeued" requests won't be locked anymore

This becomes worse if the user runs a CPU-bound thing that stalls the node.js event loop.

Possible solutions

1. ignore it
2. run a background loop that periodically prolongs all held locks
3. prolong locks in fetchNextRequest - that should be called at least once per requestHandlerTimeout