Purge dead file-backed scrubber queue code

[Chris St. Pierre]

The image location status blueprint (https://blueprints.launchpad.net/glance/+spec/image-location-status) removed the possibility to run the glance-scrubber with a file-backed queue, but didn't actually remove the code or configuration for it. We should clean up the code base and purge that dead code.

More details: http://lists.openstack.org/pipermail/openstack-dev/2015-February/056652.html

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/161051
Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=643ad31474bde9014a10f6d23055dfec9774fb3e
Submitter: Jenkins
Branch: master

commit 643ad31474bde9014a10f6d23055dfec9774fb3e
Author: Chris St. Pierre <email address hidden>
Date: Tue Mar 3 18:59:50 2015 -0600

    Purge dead file-backed scrubber queue code

    The file-backed scrubber can no longer be used (see 66d24bb), but the
    code for it is still in place, including several configuration
    options, abstraction layers, and so on. This commit removes that dead
    code.

    It also deprecates the scrubber_datadir, cleanup_scrubber, and
    cleanup_scrubber_time options, which are no longer
    functional. "Cleanup" mode is also removed, as it is now equivalent to
    the normal running mode of the scrubber.

    DocImpact
    Closes-Bug: 1427929
    Change-Id: I3c2a43acee21c685a2de3a7b67ba831548bc27df