Get CAs returns empty list

[Dave McCowan]

Even with CA plugins configured:
    a call to GET /v1/cas returns an empty list
    a call to GET /v1/cas/get-preferred returns 404

Once an order has been posted, then these calls work correctly.

The CAs database is initialized on the first post. It should be initialized when Barbican starts.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/224156

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/224156
Committed: https://git.openstack.org/cgit/openstack/barbican/commit/?id=91a561dd9adc44b89ada27104e27649e2c726a5a
Submitter: Jenkins
Branch: master

commit 91a561dd9adc44b89ada27104e27649e2c726a5a
Author: Dave McCowan <email address hidden>
Date: Wed Sep 16 11:39:30 2015 -0400

    Finish Initialization of CA Table when Barbican Starts

    Before all CA related commands can succeed, the CA table needs to
    be populated. This patch invokes code to refresh the table as
    Barbican starts.

    In addition, the CA table entries can expire over time, to ensure
    GET /cas always returns current values, the table is refreshed as
    necessary at that time too.

    I also added created a session for this routine to ensure any
    updates are written immediately to the database.

    Change-Id: I0e6f9aec073c897f811b0b87a16db3b52753d734
    Closes-bug: #1495576