Remove custom json encoder cleaner and strip proxy var stuff out before encoding

Fixes #12349

lib/ansible/utils/vars.py

@@ -20,6 +20,7 @@ from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
 import ast
+from json import JSONEncoder
 from collections import MutableMapping
 
 from six import iteritems, string_types
@@ -128,14 +129,3 @@ def isidentifier(ident):
 
     return True
 
-def json_variable_cleaner(obj):
-    '''
-    Used as the default= parameter to json.dumps(), this method helps
-    clear out UnsafeProxy variables so they can be properly JSON encoded
-    '''
-    from ansible.vars.unsafe_proxy import UnsafeProxy
-    if isinstance(obj, UnsafeProxy):
-        return obj._obj
-    else:
-        return obj
-