[ResourceBundle] fix merging request and config sorting parameters

[Strontium-90]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets
License	MIT
Doc PR

If specify default sorting order in config:

sylius_backend_country_index:
    path: /
    methods: [GET]
    defaults:
        _controller: sylius.controller.country:indexAction
        _sylius:
            template: SyliusWebBundle:Backend/Country:index.html.twig
            sortable: true
            paginate: 50
            sorting:
                name: asc

and trying sort table manually GET /administration/countries/?sorting%5BisoName%5D=asc
Query will contain:

ORDER BY o.name ASC, o.isoName ASC

but should be

ORDER BY o.isoName ASC, o.name ASC

[pjedrzejewski]

Makes sense, thank you again Aleksey!