Notices for unused dh_modulus, dh_gen and dh_consumer_public

There are two places in the code where dh_modulus and dh_gen is attempted to be used from the request. If the client is a Drupal OpenID client, these will not be provided. The second place where these are used, isset() checks lead them in. However, the first place they are neither checked neither used later in that function. Therefore it looks like entirely safe to remove them.