Send non Success StatusCode as per the spec ie. as a two-level StatusCode element.

Currently the only non Succes statuscode we use is NoPassive.

HTTPPost required a follow up fix thats prevents a runtime error
that occurs if we try to encrypt an assertion thats missing in
unsuccessfull responses 


git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@858 44740490-163a-0410-bde0-09ae8108e29a