Revert "Avoid dangerous and mysterious behaviour if someone tries to modify a config"

This reverts commit 83afb58a9a.

letsencrypt/configuration.py

@@ -43,12 +43,6 @@ class NamespaceConfig(object):
         # Check command line parameters sanity, and error out in case of problem.
         check_config_sanity(self)
 
-        # We're done setting up the attic. Now pull up the ladder after ourselves...
-        self.__setattr__ = self.__setattr_implementation__
-
-    def __setattr_implementation__(self, var, value):
-        return self.namespace.__setattr__(var, value)
-
     def __getattr__(self, name):
         return getattr(self.namespace, name)