The dead dog didn’t help, nor did a string of other security lapses large and small. But in the end, a blistering critique from her own team of managers may have been too much for the federal security director at Newark Liberty International Airport to withstand. Barbara Bonn Powell, who has held the Transportation Security Administration’s top post at Newark Liberty since January 2008, sent a staff-wide e-mail to the TSA’s 1,400 employees at the airport Tuesday, announcing she was stepping down to take a job at the agency’s headquarters in Arlington, Va. Though the TSA declined to link her...