Modify tag issuer in LogoutRequest

[Peter Schober]

* Cantor, Scott <cantor.2 at osu.edu> [2016-11-07 17:47]:
> This appears to be (as Dave said) the same misguided Italian
> federation (pretty sure it can't be GARR? the higher ed one?) asking
> you to violate the SAML specification.

I'm guessing it's for SPID
http://www.agid.gov.it/agenda-digitale/infrastrutture-architetture/spid
from the same folks (AgID) that brought us this discussion on the
OASIS saml-dev list earlier this year:
https://lists.oasis-open.org/archives/saml-dev/201606/threads.html
but I haven't checked their (Italian) specs for this weirdness yet.
-peter