Formdata should not bootstrap the folder structure

Since downstream projects can for example already bootstrap

/formdata/permanent

we do not check whether /formdata has children to add the initial structure, but whether it has at least 10 children. If not, we add the initial structure (again). Note that the initial structure is meant to minimize the risk that in the beginning when there are not yet many nodes, two visitors try to create the very same ancestors resulting in a jcr exception