ipatests: fix wrong xfail in test_domain_resolution_order
    
    The test is written for a SSSD fix delivered in 2.2.0, but has a xfail
    based on fedora version < 30.
    SSSD 2.2.0 was originally available only on fedora 30 but is now also
    available on fedora 29, and recent runs on f29 started to succeed
    (because the fix is now present) but with a strict xfail.
    
    The fix completely removes the xfail as the current branch is supported on
    fedora 29 and 30.
    
    Fixes: https://pagure.io/freeipa/issue/8052
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Sergey Orlov <sorlov@redhat.com>
    Reviewed-By: Francois Cami <fcami@redhat.com>