MAGETWO-34952: Final cleanup to ensure Core module is properly removed

- Change collection references

Author: Bryant Luk

dev/tests/functional/tests/app/Magento/Core/Test/Fixture/ConfigData.xml

@@ -10,7 +10,7 @@
            module="Magento_Core" 
            type="flat" 
            entity_type="core_config_data" 
-           collection="Magento\Core\Model\Resource\Config\Data\Collection" 
+           collection="Magento\Config\Model\Resource\Config\Data\Collection" 
            repository_class="Magento\Core\Test\Repository\ConfigData" 
            handler_interface="Magento\Core\Test\Handler\ConfigData\ConfigDataInterface" 
            class="Magento\Core\Test\Fixture\ConfigData">

dev/tests/functional/tests/app/Magento/Core/Test/Fixture/SystemVariable.xml

@@ -9,7 +9,7 @@
   <fixture name="systemVariable" 
            module="Magento_Core" 
            type="composite" 
-           collection="Magento\Core\Model\Resource\Variable\Collection" 
+           collection="Magento\Variable\Model\Resource\Variable\Collection" 
            handler_interface="Magento\Core\Test\Handler\SystemVariable\SystemVariableInterface" 
            class="Magento\Core\Test\Fixture\SystemVariable">
     <dataset name="default">