Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2017-08-30' into staging

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2017-08-30' into staging

nbd patches for 2017-08-30

- Kashyap Chamarthy: qemu-iotests: Extend non-shared storage migration test (194)
- Stefan Hajnaczi: 0/3 nbd-client: enter read_reply_co during init to avoid crash
- Vladimir Sementsov-Ogievskiy: portions of 0/17 nbd client refactoring and fixing

# gpg: Signature made Wed 30 Aug 2017 19:03:46 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-2017-08-30:
  block/nbd-client: refactor request send/receive
  block/nbd-client: rename nbd_recv_coroutines_enter_all
  block/nbd-client: get rid of ssize_t
  nbd/client: fix nbd_send_request to return int
  nbd/client: refactor nbd_receive_reply
  nbd/client: refactor nbd_read_eof
  nbd/client: fix nbd_opt_go
  qemu-iotests: test NBD over UNIX domain sockets in 083
  qemu-iotests: improve nbd-fault-injector.py startup protocol
  nbd-client: avoid read_reply_co entry if send failed
  qemu-iotests: Extend non-shared storage migration test (194)

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