[postcreate] properly set is_instance_of for bootstrap entities Entities created before CWEType itself need the is/is_instance_of relations created later. We were actually only inserting "is". Closes #7656606.

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