fixes #7253 - change nil admin field on users to false, matches usergroups

When the admin field was nil, admin_changed? in user model validations can
evaluate to true if the field changed from nil to false.
fixes #3105 - use untranslated string for PuppetCA state filter
fixes #4375: provisioning no longer loops when using oVirt + compute profile
Fixes #4596 - Change parent of host group via AJAX

Reparenting host groups requires submitting the form to see the changes
nowadays, this fix makes the host group model inherit all properties
from the parent and show them in real time.