The signature validation removes the signature element from the DOM
tree, which causes the metadata parsing to skip the DOM node following
the signature element. Normally this element would be a text node, but
it could also be a SSODescriptor-element.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1931 44740490-163a-0410-bde0-09ae8108e29a