Can't override third party serializer config file

[oatto]

I'm using symfony v2.8.4-dev and I have noticed that the overriding file didn't work anymore, because symfony doesn't bring the config key as config name.

The temporary solution that I have fixed by adding this line in JMS\SerializerBundle\DependencyInjection\Configuration

->useAttributeAsKey('name')
next to
->arrayNode('directories')
so it becomes:
->arrayNode('directories') ->useAttributeAsKey('name')

Thank you

[goetas]

duplicate of #531