_get_token_expiration in auth_token.py should return isotime

[wanghong]

Currently, _get_token_expiration method returns a normalized time, at the same time, _confirm_token_not_expired method returns an isotime, refer to: https://github.com/openstack/keystonemiddleware/blob/master/keystonemiddleware/auth_token.py#L405, https://github.com/openstack/keystonemiddleware/blob/master/keystonemiddleware/auth_token.py#L414. We will cache the expire time returned by the two methods in the _TokenCache object. But _TokenCache object treats it as an isotime when getting cache, refer to: https://github.com/openstack/keystonemiddleware/blob/master/keystonemiddleware/auth_token.py#L1877. I think _get_token_expiration should return isotime too.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/140984
Committed: https://git.openstack.org/cgit/openstack/keystonemiddleware/commit/?id=30c4794c37a2ee0d5e194465dac2c7043c62a7f9
Submitter: Jenkins
Branch: master

commit 30c4794c37a2ee0d5e194465dac2c7043c62a7f9
Author: wanghong <email address hidden>
Date: Thu Dec 11 16:59:53 2014 +0800

    iso expires should be returned in one place

    Currently, _get_token_expiration method returns a normalized time,
    at the same time, _confirm_token_not_expired method returns an isotime.
    We will cache the expire time returned by the two methods in the
    _TokenCache object. But _TokenCache object treats it as an isotime when
    getting cache.
    There are two issues here:
    1. _get_token_expiration should return isotime too
    2. expires should be returned in one place rather than in two places
    which is a gap make expires in different time-forms

    Closes-Bug: #1413093
    Change-Id: I85dbaaed0c761ff2f4bcc960df94a4e106af1730