vhost: fix virtqueue initialization

vhost: fix virtqueue initialization

This patches fixes virtqueue initialization issue causing
segfault or file descriptor being closed unexpectedly.

The wrong index was passed to init_vring_queue() by
alloc_vring_queue() when a hole in the virtqueue array was
met.

Fixes: 8acd7c213353 ("vhost: fix virtqueues metadata allocation")
Cc: stable@dpdk.org
Reported-by: Yu Jiang <yux.jiang@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Tested-by: Yu Jiang <yux.jiang@intel.com>