vhost-scsi: add missing virtqueue_size parameter

Commit 5c0919d02066 ("virtio-scsi: Add virtqueue_size parameter allowing
virtqueue size to be set.") introduced a new parameter to virtio-scsi.
Later, commit 920036106044 ("vhost-user-scsi: add missing virtqueue_size
param") added that parameter to the new vhost-user-scsi interface but
neglected the existing vhost-scsi interface it was built on.

Apply the same change to vhost-scsi, so that we can boot a guest with
a device defined.  This also avoids crashing a guest when hotplugging
a vhost-scsi device.

Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-id: 20171201151538.6844-2-farman@linux.vnet.ibm.com
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
