AD/IPA: Create kdcinfo file for sub-domains
With this patch kdcinfo files are created for sub-domains by the AD
provider and by the IPA provider on the IPA servers
(ipa_server_mode=True).
Related to https://pagure.io/SSSD/sssd/issue/3652
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>