can not set auth_endpoint in run time. (options.set_defaults)

[Sungjin Yook]

Problem statement:
================

When trying to override keytone endpoint as
      options.set_defaults(conf, auth_endpoint='http://XXX.XXX.XXX.XXX:5000/v3')

The application using castellan module errors out as shown below:

/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7 /Users/mixos/yook/gitrepos/alchemy-kms-demo/demo.py
Traceback (most recent call last):
  File "/Users/mixos/yook/gitrepos/alchemy-kms-demo/demo.py", line 75, in <module>
    options.set_defaults(conf, auth_endpoint='http://XXX.XXX.XXX.XXX:5000/v3')
TypeError: set_defaults() got an unexpected keyword argument 'auth_endpoint'

Process finished with exit code 1

Proposal:
=========
It's important that application should be able to override auth_endpoint in runtime.
Another use case is .. some application can not afford to have a configuration file under /etc/castellan. So, this ability of overriding default attribute in runtime is really valuable, especially keystone endpoint.
Adding configurables(i.e. auth_endpoint and so on) to options.set_defaults.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/244809
Committed: https://git.openstack.org/cgit/openstack/castellan/commit/?id=132200244f741aee5a887c084456f8b9c637c9cd
Submitter: Jenkins
Branch: master

commit 132200244f741aee5a887c084456f8b9c637c9cd
Author: Sungjin Yook <email address hidden>
Date: Thu Nov 12 12:33:26 2015 -0600

    Can not set auth_endpoint in runtime

    In rumtime castellan should be able to set auth_endpoint using options.set_defaults()
    which is critical for application to be able to adjust endpoint in runtime.
    https://bugs.launchpad.net/castellan/+bug/1515388

    Change-Id: Ie918dcc4d28ec3507559e1b0c218995f6809c364
    Closes-Bug: 1515388

[Kaitlin Farr (kaitlin-farr)]

This was patch was released with Castellan version 0.3.0.