SimpleSAML_Metadata_SAMLParser: Fix bug in signature validation.
SimpleSAML_Metadata_SAMLParser: Fix bug in signature validation.

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.

rchavik/simplesamlphp,rchavik/simplesamlphp,rchavik/simplesamlphp,rchavik/simplesamlphp