Add support for logout over SOAP
As each login session comes in, store the supported logout
mechanisms in the SP metadata.
Upon a logout request, loop through all of those SP's that
support SOAP and log those out first, then log out any
remaining sessions using HTTP Redirect.
https://fedorahosted.org/ipsilon/ticket/59
Signed-off-by: Rob Crittenden <rcritten@redhat.com>
Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>