Fix Flattener regression where queued filters on root table were not being executed resulting in rows of root table not having columns/metadata.

Conflicts:

	core/API/DataTableManipulator/Flattener.php
	tests/PHPUnit/Integration/expected/test_FlattenReports__CustomVariables.getCustomVariables_day.xml
	tests/PHPUnit/Integration/expected/test_FlattenReports_expandedWithDepth__Actions.getPageUrls_week.xml