vhost: fix redundant vring status change notification

vhost: fix redundant vring status change notification

When VHOST_USER_F_PROTOCOL_FEATURES is not negotiated,
there is no need for vhost_user_set_vring_kick() to
notify the application of vring enabled, as
vhost_user_msg_handler() also notifies the application.

This patch is to remove unnecessary vring_state_changed() call.

Fixes: d0fcc38f5fa4 ("vhost: improve device readiness notifications")
Cc: stable@dpdk.org
Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
Tested-by: Yinan Wang <yinan.wang@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>