Wrap Mongo cursor in `try...finally` block
Wrap Mongo cursor in `try...finally` block

(sapling split of 35a9f8e01f8a3476010d48e4eaec04ca380d9db7)
foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio