There are hugs and there are hugs.... In a restaurant from a waitress, if they are done spontaneously and without fan fare, and are not overly smoochy, and are short and sweet, I cannot see a problem with it.
I used to work in a Credit Union, as a loans officer, and had a wonderful clientelle of people who I looked after for years. We became friends became very close over the years. There were several, men and women, who often came in the office, and greeted me with a hug or even a kiss on the cheek. It was spontaneous, and affectionate, and did not embarrass anyone, or looked at as anything but a freindly gesture.
As long as there is not other agenda, other than professional freindliness, then there is nothing wrong with it.