[cwctl] do only clean static data dir content (closes #17069762) deleting the directory itself is useless and may be a problem in automated deployment environments (user may not have permissions to delete or create that directory).

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances