Set configs for glance_store

glance_store uses a new section to keep its configs. This patch
duplicates the existing, store related, config options and sets them
under the glance_store section.

Once glance is fully migrated, the old options will be removed.

Change-Id: Ie3de87cf07a321415d111e644ccbb360c7491151
Merge "Set configs for glance_store"
Merge branch 'master' of https://github.com/openstack-dev/devstack