fix two issues with virtio-blk

1. Check if blk_size is valid in virtio_blk config.
2. Disable interrupt otherwise interrupt may stuck
   with some guests.

Signed-off-by: Gleb Natapov <gleb@redhat.com>

ChangeLog:
 v1->v2:
  - Treat sector size not equal to 512 bytes as error.
3 files changed
tree: 19585cedc982324f30501e1503d07f2d3743351e
  1. .gitignore
  2. COPYING
  3. COPYING.LESSER
  4. Makefile
  5. README
  6. TODO
  7. src/
  8. tools/
  9. vgasrc/