L2SS-777: improve device_list function

docker-compose/tango-prometheus-exporter/code/tango-prometheus-client.py

@@ -43,13 +43,13 @@ class ArchiverPolicy(object):
         device_list = []
         db = Database()
         server_list = db.get_server_list()  # e.g. SDP/STAT, RECV/STAT
-        for i in range(0, len(server_list)):
+        for server in server_list:
             # https://pytango.readthedocs.io/en/stable/database.html#tango.Database.get_device_class_list
-            class_list = db.get_device_class_list(server_list[i])
-            for j in range(0, len(class_list), 2):
-                if "dserver" in class_list[j]:
+            class_list = db.get_device_class_list(server)
+            for cls in class_list[::2]:
+                if "dserver" in cls:
                     continue
-                device_list.append(class_list[j].lower())
+                device_list.append(cls.lower())
         return device_list
     
     def multimember_device_list(config_devices: list) -> list: