Description of problem:

ssd config option:
  default_domain_suffix = blah
breaks sudo.

And causes local users to show up with "implicit_files" domain.

Version-Release number of selected component (if applicable):
sssd-2.0.0-43.el8_0.3


How reproducible:
Easily.

Steps to Reproduce:
1. Configure local user to sudo eg to root without password.
2. Add "default_domain_suffix = blah" option to sssd section of sssd.conf.
3. Restart sssd.
4. Login as local user, behold as your bash prompt or whatever shows
"implicit_files" domain.
5. Try to sudo to root, as allowed by sudoers. Marvel and boggle with amazement
as it fails.

Actual results:
bash prompt:
[someuser@implicit_files@somehostname ~]$

sudo fail:
  sudo su -
  sudo: PAM account management error: Authentication service cannot retrieve
authentication info

Expected results:
bash prompt:
[someuser@somehostname ~]$

sudo su -
#success

Additional info: