PHIL STEWART and IDREES ALI A drone strike in Kabul last month killed as many as 10 civilians, including seven children, the U.S. military has revealed, apologizing for what it called a "tragic mistake". The Pentagon had said the August 29 strike targeted an Islamic State suicide bomber who posed an imminent threat to U.S.-led troops at the airport as they completed the last stages of their withdrawal from Afghanistan. Even as reports of civilian casualties emerged, the top U.S. general had described the attack as "righteous". The head of U.S. Central Command, Marine Corps General Frank McKenzie, said that…