MAGETWO-91521: Reports / Sales / Tax report show incorrect amount

- Fixed to correct db field to retrieve tax amount
- Removed incorrect calculating order subtotals and totals count in Tax report

Author: oksana-kr

app/code/Magento/Reports/Block/Adminhtml/Sales/Tax/Grid.php

@@ -123,7 +123,6 @@ protected function _prepareColumns()
             [
                 'header' => __('Orders'),
                 'index' => 'orders_count',
-                'total' => 'sum',
                 'type' => 'number',
                 'sortable' => false,
                 'header_css_class' => 'col-qty',

app/code/Magento/Tax/Model/ResourceModel/Report/Tax/Createdat.php

@@ -84,7 +84,7 @@ protected function _aggregateByOrder($aggregationField, $from, $to)
                 'order_status' => 'e.status',
                 'percent' => 'MAX(tax.' . $connection->quoteIdentifier('percent') . ')',
                 'orders_count' => 'COUNT(DISTINCT e.entity_id)',
-                'tax_base_amount_sum' => 'SUM(tax.base_amount * e.base_to_global_rate)',
+                'tax_base_amount_sum' => 'SUM(tax.base_real_amount * e.base_to_global_rate)',
             ];
 
             $select = $connection->select()->from(