Interior Secretary Ken Salazar will retire from his post at the end of March, ending a four-year stint in President Obama’s cabinet and becoming its sixth member to depart it this year. Mr. Salazar made his mark at Point Reyes National Seashore when he chose to close Drakes Bay Oyster Company last November; he is now part of a lawsuit brought by the oyster company against him and his chief of the National Park Service,…