Usually treats can make animals associate stuff with positive feelings. Maybe try throwing the dog treats every once in a while but if the dog's so anxious about you, don't approach or stroke it; just ignore it.
I haven't encountered a situation like that and can't offer any other advice than treats. However, if all the attempts to get on the dog's good side fail, can you simply tell the owner that you don't feel comfortable around this dog, and that you want him to make sure the dog can't get near you? If I were in your situation, I'd try to explain to the owner that there's a credible risk of an incident, and ask him to keep watching the dog at all times during these weekends instead of leaving it unsupervised. He knows the dog has showed aggression towards you, so it's kinda irresponsible if he's letting the dog out of his sight.
How big is the dog, anyway? Just wondering which one would be in a bigger danger if you did actually get into a fight; you or the dog.