Uses alembic migration when deploying devstack
Uses alembic migration when deploying devstack

Changes devstack to deploy the barbican database using the
alembic migrations instead of the auto-migrate feature. This allows
us to make sure any migrations do not break barbican-manage.

Closes-Bug: #1500629
Change-Id: Ia68698311c8e6ec84672701f38967d8d0016b784

openstack/barbican,openstack/barbican