Wonder if Kelly Clarkson ever imagined her wedding to be a second like this! The “American Idol” alum published on the ACM Awards on Sunday that her u . s . a . crooner good friend Blake Shelton is not going to only sing at her upcoming wedding — he’ll be officiating!Clarkson, 30, instructed “Leisure Tonight’s” Nancy O’Dell that “The Voice” mentor will conduct her wedding to fiance Brandon Blackstock (No furthe…