cms.optional and obsolete now return None from call to value()

WMAgent code was failing when dealing with the new optional and
obsolete parameter types. The code was always calling value()
which was not available on parameters which were not set.

FWCore/ParameterSet/python/Types.py

@@ -95,6 +95,11 @@ def insertInto(self, parameterSet, myname):
         v = self.__dict__.get('_ProxyParameter__value', None)
         if v is not None:
             v.insertInto(parameterSet,myname)
+    def value(self):
+        v = self.__dict__.get('_ProxyParameter__value', None)
+        if v is not None:
+            return v.value()
+        return None
 
 class _ObsoleteParameter(_OptionalParameter):
     @staticmethod