when validating issuer, look for the info on the Assertion too
when validating issuer, look for the info on the Assertion too

apparently some IdPs do that

Change-Id: Ibe8976caf958398b1871317cd04517862d5a2c8f
Reviewed-on: https://gerrit.instructure.com/152338
Tested-by: Jenkins
Reviewed-by: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

instructure/ruby-saml2,instructure/ruby-saml2