Editor’s note: This story has been updated to include information from a Pentagon spokesperson. Correction: A previous version of this story misidentified Karlin’s position. WASHINGTON — Mara Karlin, who since this summer has performed the duties of Pentagon deputy under secretary of defense for policy, announced today she’s stepping down. The announcement continues the revolving door of officials performing top policy roles within the Defense Department, amid Sen. Tommy Tuberville’s (R-AL)