Bugfix for assertContainsRow

This is a fix for when assertTableContains fails. It does so because the the assertContainsRow method in QueryTable does not load data. It fails whether I pass the QueryTable instance directly or use ```php getConnection()->createQueryTable(...)``` method as patterned from the examples.

Here is a code snippet for duplication

```php
public function testAssertTableContains()
{
    $this->assertTableContains(
        array("id" => "1", "text" => "text1"),
        new PHPUnit_Extensions_Database_DataSet_QueryTable(
            "sometable",
            "SELECT id, text FROM sometable WHERE id = 1",
            $this->getConnection()
        )
    );
}
```

Here is the error that I get before the fix

> 1) DBUnitBug::testAssertTableContains
> in_array() expects parameter 2 to be array, null given

There is already an [open issue](https://github.com/sebastianbergmann/dbunit/issues/64) about this already.