Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2017-08-23' into staging

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2017-08-23' into staging

nbd patches for 2017-08-23

- Fam Zheng: 0/4 block: Fix non-shared storage migration
- Stefan Hajnoczi: qemu-iotests: add 194 non-shared storage migration test
- Stefan Hajnoczi: nbd-client: avoid spurious qio_channel_yield() re-entry

# gpg: Signature made Wed 23 Aug 2017 17:22:53 BST
# gpg:                using RSA key 0xA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>"
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>"
# gpg:                 aka "[jpeg image of size 6874]"
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-nbd-2017-08-23:
  nbd-client: avoid spurious qio_channel_yield() re-entry
  qemu-iotests: add 194 non-shared storage migration test
  block: Update open_flags after ->inactivate() callback
  mirror: Mark target BB as "force allow inactivate"
  block-backend: Allow more "can inactivate" cases
  block-backend: Refactor inactivate check

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