Fixed bug with refreshing tokens in file Storage
diff --git a/oauth2client/django_orm.py b/oauth2client/django_orm.py
index 581fe8e..5e511db 100644
--- a/oauth2client/django_orm.py
+++ b/oauth2client/django_orm.py
@@ -86,7 +86,7 @@
     self.key_value = key_value
     self.property_name = property_name
 
-  def get(self):
+  def locked_get(self):
     """Retrieve Credential from datastore.
 
     Returns:
@@ -102,7 +102,7 @@
         credential.set_store(self)
     return credential
 
-  def put(self, credentials):
+  def locked_put(self, credentials):
     """Write a Credentials to the datastore.
 
     Args: