David McKernan is already seated at FX Buckley Steakhouse in Pembroke Street, Dublin with a glass of white wine in front of him when I arrive five minutes early. The founder of Java Republic, the hand-roasted coffee brand he sold in 2019, seems somewhat taken aback when I tell him I’ll have what he’s having. “Jesus, I didn’t know I’d be drinking today,” he says. “I’m supposed to be playing tennis later and I hate losing. I mean, I hate losing.” For the next three hours we talk in stress-inducing (for me) detail about how he somehow managed to keep…