Title: #851: Update __init__.py.in
When we are touching the code, I believe also `subdomains_provider`
is missing. Also most of the providers defaults to `id_provider`, few have other defaults
so I think it should be handled here as well. Please, see `man sssd.conf` for `*_provider`
options and add what is missing.
See the full comment at https://github.com/SSSD/sssd/pull/851#issuecomment-523104773