Incorrect parameters passed to delete_from_backend method

[Pranali Deore]

delete_from_backend(self.admin_context, uri) in this method uri should be
the first argument instead of self.admin_context.

https://github.com/openstack/glance/blob/master/glance/scrubber.py#L552
https://github.com/openstack/glance_store/blob/master/glance_store/backend.py#L273

NOTE:
As of now, in current master File Queue is not used, the method delete_from_backend() will never get called.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/126832

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/126832
Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=1af7c3419a8d8cdcb3c4927a4c6c275d618bb596
Submitter: Jenkins
Branch: master

commit 1af7c3419a8d8cdcb3c4927a4c6c275d618bb596
Author: Pranali Deore <email address hidden>
Date: Wed Oct 8 00:17:00 2014 -0700

    Incorrect parameters passed

    Incorrect parameters sequence is passed to
    delete_from_backend() method.

    delete_from_backend(self.admin_context, uri) in this
    method uri should be the first argument instead of
    self.admin_context.

    Closes-Bug:1378640
    Change-Id: Iebc30bad4f201dde75f2e8fe9b56e20c007c772b