net/virtio: fix crash when device reconnecting

net/virtio: fix crash when device reconnecting

When doing virtio device initialization, virtqueues will be reset in
server mode if ring type is packed. It will cause issue because queues
have been freed in the beginning of device initialization.

Fix this issue by checking whether device has been initialized before
reset. If device hasn't been initialized, there's no need to reset
queues.

Fixes: 6ebbf4109f35 ("net/virtio-user: fix packed ring server mode")
Cc: stable@dpdk.org
Signed-off-by: Marvin Liu <yong.liu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>