EZP-21781: ezfSolrDocumentFieldBaseTest::testGetFieldName() throws an error because of updated table structure

The Unit Test `ezfSolrDocumentFieldBaseTest::testGetFieldName()` throws an error because of the following SQL statement which assumes one column more than actually exists in the table `ezcontentobject_link`:

```php
$q4 = "INSERT INTO ezcontentobject_link VALUES( {$ezcca4->attribute( 'id' )}, $srcObjId4, 1, 123456, 0, 8, $imageId4 );";
```

This PR fixes this.

https://jira.ez.no/browse/EZP-21781

Cheers
:octocat: Jérôme