I think those kinds of drunk dreams are just another type of nightmare. I think they are a good sign, in a way, because they aren't happy dreams of drinking, they are fearsome dreams where we wake up frightened for a moment.
I still have dreams of being unprepared for final exams for classes I forgot I'd registered for. Those dreams don't have any deep meaning in a literal sense--the last university courses I took were 26 years ago.
I think the dreams just mean we value our sobriety, and the thought of losing it is frightening. I haven't had any in awhile, but if I did, I wouldn't be unduly alarmed by them.