I wouldn't worry too much, this test is probably just a sensible precaution. Many non-diabetics get fungal infections for all sorts of reasons, and they are usually very easy to treat. Do you have any of the other symptoms of diabetes (excessive thirst, tiredness, tingling toes etc?). It is possible to have diabetes without any symptoms, but if that is the case then it is likely to be at a very early stage. If you do have it then it is a very good thing if you can catch it before it starts to cause symptoms because then you could learn to manage it before it does you any harm.
Let's hope that you don't have diabetes, but If you do, then it isn't so bad. Of all of the major "incurable diseases" that you might think of, it is probably the easiest to manage. Once they get it under control, most diabetics learn to lead quite a normal life despite the diabetes. In fact, some people find that the lifestyle changes diabetes forces on you improves their general levels of health and well-being no end.