[nova] Include configuration directives for rbd storage

[SIGUSR2]

Since havana, nova has the ability to use the rbd backend for ephemeral storage. The relevant configuration lines in nova.conf are:

libvirt_images_type = rbd libvirt_Images_rbd_pool = "" libvirt_images_rbd_ceph_conf = "" rbd_user = "" rbd_secret_uuid = ""

Since RPC already supports cinder configuration for rbd backend, I would suggest enabling these options in nova.conf (via the environment)

Thank you.