Improve use of lockfile API

Remove remaining double close(2)'s.  i.e. close() before
commit_locked_index() or commit_lock_file().

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-fetch-pack.c

@@ -783,7 +783,6 @@ struct ref *fetch_pack(struct fetch_pack_args *my_args,
 			unlink(shallow);
 			rollback_lock_file(&lock);
 		} else {
-			close(fd);
 			commit_lock_file(&lock);
 		}
 	}