MAGETWO-74044: Import Products sets default behaviour as append, need add_update

Author: viktorpetryk

app/code/Magento/ImportExport/Model/Import/Entity/AbstractEntity.php

@@ -554,6 +554,7 @@ public function getBehavior()
             $this->_parameters['behavior']
         ) ||
             $this->_parameters['behavior'] != ImportExport::BEHAVIOR_APPEND &&
+            $this->_parameters['behavior'] != ImportExport::BEHAVIOR_ADD_UPDATE &&
             $this->_parameters['behavior'] != ImportExport::BEHAVIOR_REPLACE &&
             $this->_parameters['behavior'] != ImportExport::BEHAVIOR_DELETE
         ) {