Object store proxy should not require container if you pass a resource

Fix proposed to branch: master
Review: https://review.openstack.org/215264

Reviewed: https://review.openstack.org/215264
Committed: https://git.openstack.org/cgit/stackforge/python-openstacksdk/commit/?id=43f5a00ce1cac98e44b2846041c6dc12efeccdc1
Submitter: Jenkins
Branch: master

commit 43f5a00ce1cac98e44b2846041c6dc12efeccdc1
Author: Brian Curtin <email address hidden>
Date: Thu Aug 20 12:52:37 2015 -0500

    Get container off of an Object if its passed

    The previous object operations on object_store proxy were too strict on
    requiring a container argument to be passed, and in some cases they were
    too loose.

    When an Object is passed, look to see if it has a container attribute
    already set and use it if so. If that doesn't work out, look at the
    container argument, which that that point would have to be specified. If
    we get a container out of that, use it. After this, we won't be able to
    do any object operations with a container, so raise ValueError
    specifying that a container has to be provided.

    Change-Id: I6b587831321998245815fccf8f822025e83141c5
    Closes-Bug: 1487147