Like mav, I also associate the term "sunshine" with London slang, albeit a matey form of address that was quite unknown in West London, where I was raised (the matey form of address, to someone whose name was unknown to you, in those parts, was "John.")
But at no time did I ever hear it used as a form of racial abuse - or any other sort of abuse, actually. It always came across as matey; or at least, neutral.