XUI Authentication - Switching realms is not possible

Bug description

Switching from realmA to realmB is not possible via the XUI. When accepting to switch/leave realmA (by logging the user out), the authentication attempt in realmB fails.

How to reproduce the issue

1. Create two realms, e.g realmA & realmB
2. Point the browser to http://openam.example.com:18080/openam/XUI/?realm=realmA#login
3. Authenticate as demo
4. Point the browser to http://openam.example.com:18080/openam/XUI/?realm=realmB#login
5. Accept on switching the realms/logout from realmA
6. Authenticate as demo. It fails with:

"Session Upgrade fails since user is different than original authenticated user"

Expected behaviour

Authentication on realm B should be possible

Current behaviour

Switching from realmA to realmB is not possible

Work around

Re-try after the error, or refresh the page.

Code Analysis

Source code in 5.5.1:

if (forceAuth && sessionUpgrade) {
    try {
        newSession = AuthD.getSessionService().getSessionMutator(oldSession.getID());
    } catch (SessionException e) {
        throw new AuthException(AMAuthErrorCode.SESSION_UPGRADE_FAILED, e);
    }
}