D.C. United played out a relatively dull and featureless 0-0 draw with the Chicago Fire on Saturday night, but the real celebrations would come on Sunday night. The Colorado Rapids scored in the final minutes to pull out an upset over Chivas USA, 2-1, making D.C. United the first team to ever successfully defend the Supporters’ Shield. It probably wasn’t the stylish way United will have wanted to take the regular season crown, but with…