By Paul Sandle LONDON (Reuters) -British Airways-owner IAG cut back plans to ramp up short-haul flights to avoid disruption at Heathrow airport this summer, sending its shares skidding 8% on Friday after admitting it doesn’t have enough staff to cope. The company, which also owns Iberia, Vueling and Aer Lingus, has struggled with crew absences caused by the Omicron-variant of COVID-19 and a shortage of ground staff. Compounded by IT problems, flights had to be cancelled during the first quarter. Chief Executive Luis Gallego said the issues resulted in a first-quarter operating loss of 754 mill…