[Server] Update QgsServer WFST test by adding wfs feature count verifying after added

Author: rldhont

tests/src/python/test_qgsserver_wfst.py

@@ -183,6 +183,7 @@ def _checkAddFeatures(self, wfs_layer, layer, features):
         layer = self._getLayer(layer.name())
         self.assertTrue(layer.isValid())
         self.assertEqual(layer.featureCount(), len(features))
+        self.assertEqual(wfs_layer.dataProvider().featureCount(), len(features))
 
     def _checkUpdateFeatures(self, wfs_layer, old_features, new_features):
         """