vhost-user-blk: delete virtioqueues in unrealize to fix memleaks

virtio queues forgot to delete in unrealize, and aslo error path in
realize, this patch fix these memleaks, the leak stack is as follow:

Direct leak of 114688 byte(s) in 16 object(s) allocated from:
    #0 0x7f24024fdbf0 in calloc (/lib64/libasan.so.3+0xcabf0)
    #1 0x7f2401642015 in g_malloc0 (/lib64/libglib-2.0.so.0+0x50015)
    #2 0x55ad175a6447 in virtio_add_queue /mnt/sdb/qemu/hw/virtio/virtio.c:2327
    #3 0x55ad17570cf9 in vhost_user_blk_device_realize /mnt/sdb/qemu/hw/block/vhost-user-blk.c:419
    #4 0x55ad175a3707 in virtio_device_realize /mnt/sdb/qemu/hw/virtio/virtio.c:3509
    #5 0x55ad176ad0d1 in device_set_realized /mnt/sdb/qemu/hw/core/qdev.c:876
    #6 0x55ad1781ff9d in property_set_bool /mnt/sdb/qemu/qom/object.c:2080
    #7 0x55ad178245ae in object_property_set_qobject /mnt/sdb/qemu/qom/qom-qobject.c:26
    #8 0x55ad17821eb4 in object_property_set_bool /mnt/sdb/qemu/qom/object.c:1338
    #9 0x55ad177aeed7 in virtio_pci_realize /mnt/sdb/qemu/hw/virtio/virtio-pci.c:1801

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200224041336.30790-2-pannengyuan@huawei.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>