ipatests: mark test_smb as xfail
Mark the test test_smb.py::TestSMB::test_smb_service_s4u2self as xfail.
Related: https://pagure.io/freeipa/issue/9124
Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>