ipatests: add xfail for autoprivate group test with override
    
    Because of SSSD issue 7169, secondary groups are not
    retrieved when autoprivate group is set and an idoverride
    replaces the user's primary group.
    Mark the known issues as xfail.
    
    Related: https://github.com/SSSD/sssd/issues/7169
    
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Anuja More <amore@redhat.com>