KAMPALA — Birabwa Hajara’s braids are long enough to reach her hips if she let them down. But she doesn’t. “Some jobs limit our freedom of expression. A driver cannot let her long hair loose. It will be prickly,” she says. Instead, she ties the braids into a knot above her head, a style whose shape has earned it the local nickname “doughnut.” It’s 5 a.m., still a little dark, and the 42-year-old is already up and about on her first job as a school driver. At gates to homes in different neighborhoods, she stops and honks. Schoolchildren hop into her school bus. She will drive them to Taibah Int…