Catch unsigned logout requests and raise a 400 for now
A 400 is still going to blow up the logout sequence but
it is better than a 500 and at least tells the user what
This is most likely to be run into during initial SP
testing and not in production.
Signed-off-by: Rob Crittenden <email@example.com>
Reviewed-by: Patrick Uiterwijk <firstname.lastname@example.org>