Title: #419: sudo: document background activity
When we introduced socket activation, we changed the internall behaviour.
Previously we disabled sudo if it was not listed in services, with
socket activation we removed this feature. Some users were confused
so this change documents current behaviour.
To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/419/head:pr419
git checkout pr419