Optimize: Reuse device instance in the same function

- Speed up retire confirm
- Set default server to CN
- Improve log appearance of aScreenCap init

module/config/server.py

@@ -2,4 +2,4 @@
 This file stores server, such as 'cn', 'en'.
 Use 'import module.config.server as server' to import, don't use 'from xxx import xxx'.
 """
-server = 'default'
+server = 'cn'  # Setting default to cn, will avoid errors when using dev_tools