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-update-index.c

@@ -738,7 +738,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 			    get_index_file(), strerror(lock_error));
 		}
 		if (write_cache(newfd, active_cache, active_nr) ||
-		    close(newfd) || commit_locked_index(lock_file))
+		    commit_locked_index(lock_file))
 			die("Unable to write new index file");
 	}