This patch originates from the patch:
"Patch for Qemu wrapper for US-VHost to ensure Qemu process ends when
VM is shutdown", http://dpdk.org/ml/archives/dev/2014-June/003606.html
Also update the vhost sample guide doc.
Signed-off-by: Claire Murphy <claire.k.murphy@intel.com>
Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>