Support boot from volume for Kubernetes all nodes (master and worker)
so that user can create a big size root volume, which could be more
flexible than using docker_volume_size. And user can specify the
volume type so that user can leverage high performance storage, e.g.
NVMe etc.
And a new label etcd_volme_type is added as well so that user can
set volume type for etcd volume.
If the boot_volume_type or etcd_volume_type are not passed by labels,
Magnum will try to read them from config option
default_boot_volume_type and default_etcd_volume_type. A random
volume type from Cinder will be used if those options are not set.
Task: 30374
Story: 2005386
Co-Authorized-By: Feilong Wang<flwang@catalyst.net.nz>
Change-Id: I39dd456bfa285bf06dd948d11c86867fc03d5afb
6788a99e71