Only apply spyne monkey patch if needed

git-svn-id: https://humgenprojects.lumc.nl/svn/mutalyzer/branches/spyne@581 eb6bd6ab-9ccd-42b9-aceb-e2899b4a52f1

mutalyzer/util.py

@@ -896,6 +896,9 @@ def monkey_patch_spyne():
     """
     from spyne.model.fault import Fault
 
+    if hasattr(Fault, '_to_dict'):
+        return
+
     def _to_dict(self, *args, **kwargs):
         return dict(Fault=dict(faultcode=self.faultcode,
                                faultstring=self.faultstring))