vhost: fix device cleanup at stop
vhost: fix device cleanup at stop

This prevents from destroying & recreating user device in "incomplete"
vring state. virtio_is_ready() was returning true for devices with
vrings which did not have valid callfd (their VHOST_USER_SET_VRING_CALL
hasn't arrived yet)

Fixes: 8f972312b8f4 ("vhost: support vhost-user")
Cc: stable@dpdk.org

Signed-off-by: Dariusz Stojaczyk <f11d01fc0f74696e7ca69a73f989fd3bd0b37668@intel.com>
Signed-off-by: Tomasz Kulasek <2fc2c8542a2a68801ce1aaca56eae5adf14485ae@intel.com>
Reviewed-by: Jianfeng Tan <4339d9ba3a87a0d192e405945005ff86667f7b0c@intel.com>
Reviewed-by: Maxime Coquelin <9a2667dee3b90866bbc9c2696cff2b7d5616c95a@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk