Revert "Merge pull request #73 from thread/limit-keys-calls-on-startup"

This reverts commit 04b985f, reversing
changes made to 6ff4b90.

While using SCAN instead of KEYS is the recommended approach, it
turns out that it has worse real-world behaviour in the scenario
that the change was intended to make. Specifically the queue start-up
times were observed to be much longer while the load on the redis
instance was not reduced meaningfully, negatively impacting other
clients worse than when KEYS was used.

Author: PeterJCLaw

django_lightweight_queue/backends/reliable_redis.py

@@ -55,7 +55,7 @@ def startup(self, queue: QueueName) -> None:
         # Without this the startup process can end up racing against workers on
         # other machines which are validly re-populating their processing queues
         # as they work on jobs.
-        current_processing_queue_keys = set(self.client.scan_iter(pattern))
+        current_processing_queue_keys = set(self.client.keys(pattern))
         expected_processing_queue_keys = set(
             self._processing_key(queue, worker_number).encode()
             for worker_number in get_worker_numbers(queue)