Using a kolla_logs volume ensures that logs are persistent beyond the
lifespan of the bifrost_deploy container. This is necessary to support
upgrading the bifrost services. It also opens the possibility of log
forwarding, although we do not currently deploy a fluentd container on
the bifrost host.

Change-Id: If3118cd75ccc87b0d003d5f382695aeaa43ed0f8
Partially-implements: blueprint bifrost-upgrade