Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

# gpg: Signature made Tue 12 Feb 2019 03:58:58 GMT
# gpg:                using RSA key 9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  virtio-blk: cleanup using VirtIOBlock *s and VirtIODevice *vdev
  qemugdb/coroutine: fix arch_prctl has unknown return type
  iothread: fix iothread hang when stop too soon

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>