fix cli-script.c

fix cli-script.c

read_command_lines_1 had some (IMNSHO) spaghetti-ish code for cleanup
handling.  This makes the code much simpler to understand, by
introducing an outer cleanup.

This is another case where a stylistic change for the checker is also
nice for the reader.

	* cli/cli-script.c (read_command_lines_1): Use a null cleanup
	for 'old_chain'.  Do not check 'head' before processing
	cleanups.