BZ-1105330: Fixing SSO support in the NegotiationAuthenticator for fallback to form authentication

[SECURITY-820] Fixing SSO support in the NegotiationAuthenticator for fallback to form authentication

Jira: https://issues.jboss.org/browse/SECURITY-820
BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1105330
No upstream required