MIAMI — Iggy Azalea experienced some on-the-ground turbulence at Miami International Airport last week. The “Fancy” singer tweeted that American Airlines stranded her in the Magic City while she was traveling with her 2-year-old son, Onyx. The 31-year-old Aussie started her April 18 post warning other families to be careful when booking with the Dallas-based carrier if they have young kids. “I was flying with my son and they sold our seats while the gate was still open, then refused to take our bags off the plane although every other flight was sold out for that night,” Azalea fumed. AA replie…