Accept -1 or 1 as # of rows on insert.

While we generally want 1 row, SQLserver will return -1 as we are using
OUTPUT in insert queries now.

Refs #5104

src/ORM/Table.php

@@ -1323,7 +1323,7 @@ protected function _insert($entity, $data) {
 			->values($data)
 			->execute();
 
-		if ($statement->rowCount() > 0) {
+		if ($statement->rowCount() !== 0) {
 			$success = $entity;
 			$entity->set($filteredKeys, ['guard' => false]);
 			foreach ($primary as $key => $v) {