Ephemeral Storage Volume

Currently there are two storage supports for mysql: Volume (remote) and root partition (local). There is a flag in the conf file that toggles between these two type of storages: reddwarf_volume_support

What we also need is a way to store mysql in a ephemeral drive. The instance would boot with a flavor that specify a ephemeral storage size, which would then appear as another partition and be mounted to /var/lib/mysql.

When an instance is booted with a flavor that contains a ephemeral, the device will appear as 'vdb' just like cinder volumes.

The "reddwarf_volume_support" flag can still be used. When this variable is set to False, we will rely on the device_path to see if there is a different partition (ephemeral) available in the instance. If a device_path is specified, the instance will use that partition. If device_path == None, then the root partition will be used

Gerrit topic: https://review.openstack.org/#q,topic:bp/ephemeral-storage-volume,n,z

Addressed by: https://review.openstack.org/28751
    Add flavor API support for ephemeral