Fixing minor issues with default listing

[ryan-summers]

When deserializing, the MAC is skipped, and we need to set it so we know the default UID. Otherwise, the defaults show the MAC as 00-00-00-00-00-00. After the change:

PS C:\Users\rsummers> python -m serial COM22
--- Miniterm on COM22  9600,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---

Input was empty?

> list
Available items:
/broker: "mqtt" [default: "mqtt"]
/id: "04-91-62-d2-a8-6f" [default: "04-91-62-d2-a8-6f"]