Move base_dir_name option to somewhere more central

[OpenStack Infra]

https://review.openstack.org/55494
commit 26e861c81654ce182bedf38744c06e429b724d71
Author: Michael Still <email address hidden>
Date: Wed Nov 6 12:36:07 2013 +1100

    Move base_dir_name option to somewhere more central

    The VMWare hypervisor driver is using the base_dir_name flag, but
    it was defined in the libvirt driver. Given I am moving flags for
    libvirt into a libvirt group, this flag needs to move somewhere
    more central. It has also been renamed to the more descriptive
    image_cache_subdirectory_name.

    Progresses blueprint libvirt-opts-group.

    DocImpact: the base_dir_name flag has been renamed
    image_cache_subdirectory_name, although the old name will continue
    to work for the forseeable future.

    Change-Id: If016456b9f571ff0ec88621bd17e463faeef95ba

[Lana (loquacity)]

This flag isn't listed in any current document, so closing the doc bug.

[Lana (loquacity)]

My bad, this needs to be included in the Config Ref Guide, which is autogenerated a la https://github.com/openstack/openstack-doc-tools/tree/master/autogenerate-config-docs

[Andreas Jaeger (jaegerandi)]

Autogeneration has been done.