Fix logging out with HTTP-SOAP and HTTP-POST.
Fix logging out with HTTP-SOAP and HTTP-POST.

kviktor/djangosaml2-py3,GradConnection/djangosaml2,WiserTogether/djangosaml2,advisory/djangosaml2_tenant,shabda/djangosaml2,GradConnection/djangosaml2,City-of-Helsinki/djangosaml2,WiserTogether/djangosaml2,kviktor/djangosaml2-py3,advisory/djangosaml2_tenant,City-of-Helsinki/djangosaml2,shabda/djangosaml2