Revert "Fix backend validation of LdapBackendForm"

This reverts commit 0777848a84d63d10c5b184476845da32e92236ea.
Fix that `type' is missing for installed ldap authentication backends

refs #7163
Fix that the LdapDiscoveryForm discovers only MSAD hosts

refs #7163
Fix authentication backend validation
Fix incorrect form fields being displayed when no database resource exists
Fix that it is not possible to create an autologin auth backend

Occured only when no database resource nor a ldap resource exists.