Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2017-11-09' into staging

nbd patches for 2017-11-09

- Vladimir Sementsov-Ogievskiy: nbd/server: fix nbd_negotiate_handle_info
- Eric Blake: 0/7 various NBD fixes for 2.11

# gpg: Signature made Thu 09 Nov 2017 16:56:58 GMT
# 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-2017-11-09:
  nbd/server: Fix structured read of length 0
  nbd-client: Stricter enforcing of structured reply spec
  nbd-client: Short-circuit 0-length operations
  nbd: Fix struct name for structured reads
  nbd/client: Nicer trace of structured reply
  nbd-client: Refuse read-only client with BDRV_O_RDWR
  nbd-client: Fix error message typos
  nbd/server: fix nbd_negotiate_handle_info

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