This patch adds support reply-ack vhost-user protocol
feature, which is for now only used to ensure
VHOST_USER_SET_MEM_TABLE requests are handled by the
slave, but later will be used for VHOST_USER_SET_STATUS.
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>