As cloud-hypervisor/vhost crate (dragonball branch) is ready to be used,
switch vhost_rs from internal crate to the external one.
Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>
Extract the majority of the code that provides the vhost-user-block
backend into its own crate and port the binary to use it.
Signed-off-by: Rob Bradford <robert.bradford@intel.com>