VMware: ephemeral disk support

This patch ensures that the driver honors the following for
ephemeral disks:
 1. the flavor definition
 2. the block device mappings

The driver will now create an ephemeral disk(s) if necessary.

The ephemeral disks will be of a 'thin' disk type.

Closes-bug: #1369254

This is part of blueprint vmware-ephemeral-disk-support

DocImpact
  - Indicate that ephemeral disks are now supported by the driver

Change-Id: Icb1796e58126a1e03613946b0f5a917d6eb4708e
object-ify flavors manager side of the RPC

This change completes the conversion of flavors to use objects instead
of direct database access. The rpcapi sends objects for the new version
and primitivized data is sent for older versions.

Related to blueprint kilo-objects

Change-Id: Ib876f276cff99a21c5bca1c9f062a6c221a783e8
Merge "VMware: ephemeral disk support"
Merge "object-ify flavors manager side of the RPC"