MINOR: listener: split dequeue_all_listener() in two

MINOR: listener: split dequeue_all_listener() in two

We use it half times for the global_listener_queue and half times
for a proxy's queue and this requires the callers to take care of
these. Let's split it in two versions, the current one working only
on the global queue and another one dedicated to proxies for the
per-proxy queues. This cleans up quite a bit of code.