When user 'root' login, don't load user 'root' cache file
root is in the default_excludes list, so when accountsservice daemon startup, daemon doesn't load user
root cache file if user
root has cache file in /var/lib/Accounsservice/users.
On gnome click 'Not listed?" button to login as user
root, accountsservice still doesn't load cache file. This make user
root login always as default session, not the saved session in cache file.