KABUL — Two men convicted of slaughtering 40 people during a bank robbery in February were hanged Monday morning inside a Kabul prison, the first such sentence carried out by the government of President Hamid Karzai since the end of Taliban rule a decade ago. The government has been reluctant to administer capital punishment in an effort to distance itself from the Taliban, who carried out primitive public executions by stoning and shooting in crowded public stadiums.