authconfig.py: restore user-nsswitch.conf at uninstall time
    
    Calling authselect at uninstall time before restoring user-nsswitch.conf
    would result in a sudoers entry in nsswitch.conf which is not activated
    in the default sssd authselect profile.
    Make sure user-nsswitch.conf is restored before calling authselect.
    
    Fixes: https://pagure.io/freeipa/issue/8054
    Signed-off-by: François Cami <fcami@redhat.com>
    Reviewed-By: Thomas Woerner <twoerner@redhat.com>