RBD support was not part of BFV support, as booting using a
ceph block device was removed from the specification for BFV
as it is highly ramdisk dependent and support for booting from
such devices is unlikely to ever land in some of the available
ramdisk boot tools, muchless ironic or integrated tooling.
Change-Id: I9ddea3ae691240524aa6b946e1a513104a3f7113