Change SAML2 sessions backend to use Store API
The basic session API remains the same, just replace
the calls to pull data out of the user session to
instead pull from the database.
The per-session logout state is now a constant rather than
being a member of either the logged_in or logging_out
dictionaries.
https://fedorahosted.org/ipsilon/ticket/90
Signed-off-by: Rob Crittenden <rcritten@redhat.com>
Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>