Introduce isleaf to deviceData

Add the isleaf attribute to the deviceData attribute to make it clear in the device tree when it is a leaf node in the device tree.

pyanaconda/modules/storage/devicetree/viewer.py

@@ -142,6 +142,7 @@ def _set_device_data(self, device, data):
 
         if isinstance(device, PartitionDevice):
             data.attrs["partition-type-name"] = self._get_attribute(device, "part_type_name")
+            data.attrs["isleaf"] = self._get_attribute(device, "isleaf")
 
     def _set_device_data_dasd(self, device, data):
         """Set data for a DASD device."""