When Carrie Underwood’s band broke into the opening strains of “Sweet Child o’ Mine” at the Stagecoach Festival Saturday, it seemed like business as usual. The country superstar’s Guns N’ Roses fangirl-ism is well known, and she’s incorporated GNR numbers into her set on a regular basis before, even showing an aptitude for appropriating Axl Rose’s snaky frontman moves as her own.