One by one the tour buses descended on the blue collar neighborhood in Hong Kong known as To Kwa Wan — literally translated as Potato Bay — unloading throngs of travelers from mainland China outside large restaurants where a quick lunch awaited them inside. Outfitted in white, red and orange ball caps to denote which tour they belonged to, the visitors crowded the sidewalks, smoked cigarettes under a “No Smoking” sign and bumped into the glass storefront of a real estate office where Nicky Lam, a property agent, was rolling…