ABU DHABI, United Arab Emirates — Not long after sunrise one recent morning, a camel race here began, as they all do, with two starts. First, there was the expected opening: About a dozen camels pressed their noses against a dangling metal barrier, and when a man in a sparkling white robe gave the signal, the gate lifted and the herd surged forward, necks bobbing and humps hopping as spindly legs galloped off into the fog.