Fixed issue with multiple locales in TranslatableMapBuilder

This PR solves an issue with multiple locales of Resource Element. 
Previously only first one localization was set to the database.
i think this whole method body could be:
```php
$translatedKey = $this->translateKey($key);
if (isset($this->translatedKeys[$translatedKey]))  {
    return $translatedKey;
}

return $key;
```

due to: https://github.com/fsi-open/admin-translatable-bundle/pull/24/files#diff-cd65fbad861fa622997de0bb38f5d594R196