Filter private_token and password_confirmation params from logs.

Closes #1770.

config/application.rb

@@ -31,7 +31,7 @@ module Gitlab
     config.encoding = "utf-8"
     # Configure sensitive parameters which will be filtered from the log file.
-    config.filter_parameters.push(*[:password])
+    config.filter_parameters.push(:password, :password_confirmation, :private_token)
     # Enable escaping HTML in JSON.
     config.active_support.escape_html_entities_in_json = true