Set short timeout on first Redis pop

The previous code was always triggering a long timeout, even when
executed with the exit_on_empty_queues option. This commit uses a shorter
timeout until the first time the queues are empty.

This is really useful for tests, as most of them are obviously launched with
the exit_on_empty_queues option set: it saves 5 seconds for each test relying
on Redis queues.

azafea/processor.py

@@ -59,15 +59,18 @@ def run(self) -> None:
         queues = tuple(self.config.queues.keys())
         log.debug('{%s} Pulling from event queues: %s', self.name, queues)
 
+        timeout = 0.1
+
         while self._continue:
-            result = self._redis.brpop(queues, timeout=5)
+            result = self._redis.brpop(queues, timeout=timeout)
 
             if result is None:
                 if self.config.main.exit_on_empty_queues:
                     log.info('{%s} Event queues are empty, exiting', self.name)
                     break
 
                 log.debug('{%s} Pulled nothing from the queues and timed out', self.name)
+                timeout = 5
                 continue
 
             queue, value = result