[c-c create] make post-create step optional (closes #2712041) In this context the "post-create" step refers to the database's creation and initialization. We want to be able to create a new instance but skip the database creation (`db-create` and `db-init` commands) in automatic setup.

#!/bin/sh -e
if [ "$1" = "purge" ] ; then
        update-rc.d cubicweb remove >/dev/null
fi
 
#DEBHELPER#
 
exit 0