* This parameter will be optional and users will be able to select
a supported driver, otherwise the default configuration will be
used.
* Add docker storage driver enum field to baymodel
* Add db upgrade file
* Update heat templates for kubernetes and swarm allowing only
devicemapper and overlay as docker_storage_driver values.
* Add configuration for OverlayFS on Fedora Atomic, if overlay is
incompatible bay creation will result a CREATE_FAILED status.
* Factor out configuration of docker storage drivers
* Update tests
* Add Release Notes
Partially-Implements: blueprint support-for-different-docker-storage-driver
Change-Id: Ib58cb734c4e9c90d5d83574852213d2e97359e92
dec85b538f