Saved request parameters are not restored on relogin

Steps to reproduce:

1. Start editing a page in a tab, enter some text
2. Log out in another tab
3. Click "Save & Continue" in the first tab, you'll be redirected to login page
4. Enter user name & password, click log in, you'll be redirected to the page you were editing
5. The changes are lost

This bug was introduced in 2.4, probably by XWIKI-5317