Unused methods in quantum.wsgi clean up

Remove broken unused methods:
* wsgi.XMLDeserializer.extract_text,
* wsgi.XMLDeserializer.find_first_child_named,
* wsgi.XMLDeserializer.find_first_child_named,
* wsgi.XMLDictSerializer._create_link_nodes.

Change-Id: If00af68683571285adb0516d8fc36790bd83ffa5
Fixes: bug #1119262
Merge "Unused methods in quantum.wsgi clean up"