When Redirect action is set for Form submission in Form Builder inside a project that has a multisite setup and form is submitted on the frontend in SiteAccess with root location different than the top location, User will be redirected to the content with additional parts in the URL, resulting in 404 error.

Steps to reproduce
1. Clean installation of eZ Platform 2.5
2. Add admin.localsite.en, localsite.en and localsite.de to your system host file pointing to 127.0.0.1.
3. In the Backoffice in root location / create two LandingPages: Site EN, and Site PL. Publish both of them. Site EN will have Location id 56, and Site PL 57.
4. In ezplatform.yml:

ezpublish:
    # ...
    siteaccess:
        list: [site_en, site_pl, admin]
        groups:
            site_group: [site_en, site_pl]
            admin_group: [admin]
        default_siteaccess: site_en
        match:
            Map\Host:
                localsite.pl: site_pl
                localiste.en: site_en
                admin.localsite.com: admin
    system:
        # ...
        site_en:
            languages: [eng-GB]
            content:
                tree_root:
                    location_id: 56
                    excluded_uri_prefixes: [ /media, /images ]
        site_pl:
            languages: [eng-GB]
            content:
                tree_root:
                    location_id: 57
                    excluded_uri_prefixes: [ /media, /images ]

5. In the Backoofice, as a subitem of Site PL create a new Landing Page Test Page. Publish it.
6. Create a new Form Test Form. Set Redirect action on submit pointing to the Test Page. Publish it.
7. Add Test Form to the Test Page. Publish it.
8. Go to localsite.pl. Submit the form.

Result
After submitting the form you will be redirected to http://localsite.pl/site-pl/test-page which will result in 404 Not Found Exception

Expected Result
After submitting the form you will be redirected to http://localsite.pl/test-page