CHICAGO — Mayor Rahm Emanuel has rejected three finalists recommended by the Chicago police board for the city’s top police post and selected the force’s current chief of patrol as the new interim police superintendent, city council officials said Sunday. Emanuel is trying to replace Superintendent Garry McCarthy whose firing was part of a frantic effort to regain trust in the police department and his own leadership following the release in November of dashcam video showing a white police officer fatally shooting an unarmed black teenager 16 times. Alderman Anthony Beale said the mayor’s office called him Saturday to inform him that Emanuel has selected Chicago Chief of Patrol Eddie Johnson as interim superintendent.