aaa: filters: add Prefer new-auth option

this enforces opening a new http session, this is useful when remote
wants to enforce new session and authorization in persist mode.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1161734
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1161730
Change-Id: I78e91d9c1994203bd4b278d878b26c843eaad3cf
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>