update test for root level dataset properties

In OpenZFS 2.3 the meaning of xattr=on changed from dir to sa
which means that "ON" is now the expected value for the top-level
dataset of a new zpool.

tests/api2/test_006_pool_and_sysds.py

@@ -239,7 +239,7 @@ def test__check_root_level_dataset_properties():
     ds = call('pool.dataset.get_instance', pool_name)
     assert ds['acltype']['value'] == 'POSIX'
     assert ds['aclmode']['value'] == 'DISCARD'
-    assert ds['xattr']['value'] == 'SA'
+    assert ds['xattr']['value'] == 'ON'
     assert ds['deduplication']['value'] == 'OFF'
     assert ds['casesensitivity']['value'] == 'SENSITIVE'
     assert ds['compression']['value'] == 'LZ4'