ATLANTA — Atlanta officials have reached a $19.5 million preliminary deal to buy the property of one of two churches needed to build a new stadium for the Atlanta Falcons, Mayor Kasim Reed said Tuesday. The agreement to buy Friendship Baptist Church using money from the Atlanta Falcons amounts to a partial victory for stadium supporters. To complete the deal, the Georgia World Congress Center Authority would still need to reach an agreement with a separate church, Mount Vernon Baptist Church.