how-to.pl and how-to.tt not removed when terminating ktd

See https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=34915 for full description.

In short, when ktd up there are files that are added to the koha git. When ktd down those files are not removed.

And https://stackoverflow.com/questions/41451159/how-to-execute-a-script-when-i-terminate-a-docker-container

I remove them manually right now.