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.