Title: #255: Use default configuration with missing sssd.conf
Description of this option really doesn't say anything about missing configuration
file, but users interpretation may be vague. However, I believe we can go with this, since
if configuration file is missing but sssd is still run on start up (but is not supposed
to) it should be just disabled on systemd level...
See the full comment at https://github.com/SSSD/sssd/pull/255#issuecomment-300455385